diff --git a/gfx/layers/wr/WebRenderLayerManager.cpp b/gfx/layers/wr/WebRenderLayerManager.cpp
index c29517c6966c..f32517f3e67a 100644
--- a/gfx/layers/wr/WebRenderLayerManager.cpp
+++ b/gfx/layers/wr/WebRenderLayerManager.cpp
@@ -366,7 +366,7 @@ void WebRenderLayerManager::EndTransactionWithoutLayer(
         *mDLBuilder, resourceUpdates, aDisplayList, aDisplayListBuilder,
         mScrollData, std::move(aFilters));
 
-    aDisplayListBuilder->NotifyAndClearScrollFrames();
+    aDisplayListBuilder->NotifyAndClearScrollContainerFrames();
 
     builderDumpIndex = mWebRenderCommandBuilder.GetBuilderDumpIndex();
     containsSVGGroup = mWebRenderCommandBuilder.GetContainsSVGGroup();
diff --git a/gfx/layers/wr/WebRenderScrollData.cpp b/gfx/layers/wr/WebRenderScrollData.cpp
index b133d0c6bd2b..d3438ede7728 100644
--- a/gfx/layers/wr/WebRenderScrollData.cpp
+++ b/gfx/layers/wr/WebRenderScrollData.cpp
@@ -74,7 +74,8 @@ void WebRenderLayerScrollData::Initialize(
       Maybe<ScrollMetadata> metadata =
           asr->mScrollContainerFrame->ComputeScrollMetadata(
               aOwner.GetManager(), aItem->Frame(), aItem->ToReferenceFrame());
-      aOwner.GetBuilder()->AddScrollFrameToNotify(asr->mScrollContainerFrame);
+      aOwner.GetBuilder()->AddScrollContainerFrameToNotify(
+          asr->mScrollContainerFrame);
       if (metadata) {
         MOZ_ASSERT(metadata->GetMetrics().GetScrollId() == scrollId);
         mScrollIds.AppendElement(aOwner.AddMetadata(metadata.ref()));
diff --git a/layout/base/DisplayPortUtils.cpp b/layout/base/DisplayPortUtils.cpp
index 008159baed44..f63a334a5918 100644
--- a/layout/base/DisplayPortUtils.cpp
+++ b/layout/base/DisplayPortUtils.cpp
@@ -73,7 +73,8 @@ DisplayPortMargins DisplayPortMargins::ForContent(
 }
 
 ScreenMargin DisplayPortMargins::GetRelativeToLayoutViewport(
-    ContentGeometryType aGeometryType, nsIScrollableFrame* aScrollableFrame,
+    ContentGeometryType aGeometryType,
+    ScrollContainerFrame* aScrollContainerFrame,
     const CSSToScreenScale2D& aDisplayportScale) const {
   // APZ wants |mMargins| applied relative to the visual viewport.
   // The main-thread painting code applies margins relative to
@@ -82,7 +83,7 @@ ScreenMargin DisplayPortMargins::GetRelativeToLayoutViewport(
   // magnitude of the translation depends on whether we are
   // applying the displayport to scrolled or fixed content.
   CSSPoint scrollDeltaCss =
-      ComputeAsyncTranslation(aGeometryType, aScrollableFrame);
+      ComputeAsyncTranslation(aGeometryType, aScrollContainerFrame);
   ScreenPoint scrollDelta = scrollDeltaCss * aDisplayportScale;
   ScreenMargin margins = mMargins;
   margins.left -= scrollDelta.x;
@@ -106,7 +107,7 @@ std::ostream& operator<<(std::ostream& aOs,
 
 CSSPoint DisplayPortMargins::ComputeAsyncTranslation(
     ContentGeometryType aGeometryType,
-    nsIScrollableFrame* aScrollableFrame) const {
+    ScrollContainerFrame* aScrollContainerFrame) const {
   // If we are applying the displayport to scrolled content, the
   // translation is the entire difference between the visual and
   // layout offsets.
@@ -122,15 +123,14 @@ CSSPoint DisplayPortMargins::ComputeAsyncTranslation(
   // with it. We want only the remaining delta, i.e. the offset of
   // the visual viewport relative to the (async-scrolled) layout
   // viewport.
-  if (!aScrollableFrame) {
+  if (!aScrollContainerFrame) {
     // Displayport on a non-scrolling frame for some reason.
     // There will be no divergence between the two viewports.
     return CSSPoint();
   }
   // Fixed content is always fixed to an RSF.
-  MOZ_ASSERT(aScrollableFrame->IsRootScrollFrameOfDocument());
-  nsIFrame* scrollFrame = do_QueryFrame(aScrollableFrame);
-  if (!scrollFrame->PresShell()->IsVisualViewportSizeSet()) {
+  MOZ_ASSERT(aScrollContainerFrame->IsRootScrollFrameOfDocument());
+  if (!aScrollContainerFrame->PresShell()->IsVisualViewportSizeSet()) {
     // Zooming is disabled, so the layout viewport tracks the
     // visual viewport completely.
     return CSSPoint();
@@ -145,12 +145,13 @@ CSSPoint DisplayPortMargins::ComputeAsyncTranslation(
       // mVisualOffset, and using it to adjust the visual viewport size here.
       // Note that any incorrectness caused by this will only occur transiently
       // during async zooming.
-      CSSSize::FromAppUnits(scrollFrame->PresShell()->GetVisualViewportSize())};
+      CSSSize::FromAppUnits(
+          aScrollContainerFrame->PresShell()->GetVisualViewportSize())};
   const CSSRect scrollableRect = CSSRect::FromAppUnits(
-      nsLayoutUtils::CalculateExpandedScrollableRect(scrollFrame));
+      nsLayoutUtils::CalculateExpandedScrollableRect(aScrollContainerFrame));
   CSSRect asyncLayoutViewport{
       mLayoutOffset,
-      CSSSize::FromAppUnits(aScrollableFrame->GetScrollPortRect().Size())};
+      CSSSize::FromAppUnits(aScrollContainerFrame->GetScrollPortRect().Size())};
   FrameMetrics::KeepLayoutViewportEnclosingVisualViewport(
       visualViewport, scrollableRect, /* out */ asyncLayoutViewport);
   return mVisualOffset - asyncLayoutViewport.TopLeft();
@@ -744,7 +745,7 @@ bool DisplayPortUtils::FrameHasDisplayPort(nsIFrame* aFrame,
   if (!aFrame->GetContent() || !HasDisplayPort(aFrame->GetContent())) {
     return false;
   }
-  nsIScrollableFrame* sf = do_QueryFrame(aFrame);
+  ScrollContainerFrame* sf = do_QueryFrame(aFrame);
   if (sf) {
     if (aScrolledFrame && aScrolledFrame != sf->GetScrolledFrame()) {
       return false;
@@ -900,12 +901,12 @@ void DisplayPortUtils::ExpireDisplayPortOnAsyncScrollableAncestor(
     if (!frame) {
       break;
     }
-    nsIScrollableFrame* scrollAncestor =
+    ScrollContainerFrame* scrollAncestor =
         nsLayoutUtils::GetAsyncScrollableAncestorFrame(frame);
     if (!scrollAncestor) {
       break;
     }
-    frame = do_QueryFrame(scrollAncestor);
+    frame = scrollAncestor;
     MOZ_ASSERT(frame);
     if (!frame) {
       break;
diff --git a/layout/base/DisplayPortUtils.h b/layout/base/DisplayPortUtils.h
index feeb7c1875d7..7ffabfbf154e 100644
--- a/layout/base/DisplayPortUtils.h
+++ b/layout/base/DisplayPortUtils.h
@@ -102,15 +102,17 @@ struct DisplayPortMargins {
   // applied to (or, in the case of fixed content), the scroll frame wrt. which
   // the content is fixed.
   ScreenMargin GetRelativeToLayoutViewport(
-      ContentGeometryType aGeometryType, nsIScrollableFrame* aScrollableFrame,
+      ContentGeometryType aGeometryType,
+      ScrollContainerFrame* aScrollContainerFrame,
       const CSSToScreenScale2D& aDisplayportScale) const;
 
   friend std::ostream& operator<<(std::ostream& aOs,
                                   const DisplayPortMargins& aMargins);
 
  private:
-  CSSPoint ComputeAsyncTranslation(ContentGeometryType aGeometryType,
-                                   nsIScrollableFrame* aScrollableFrame) const;
+  CSSPoint ComputeAsyncTranslation(
+      ContentGeometryType aGeometryType,
+      ScrollContainerFrame* aScrollContainerFrame) const;
 };
 
 struct DisplayPortMarginsPropertyData {
diff --git a/layout/base/PresShell.cpp b/layout/base/PresShell.cpp
index 3ded11dd1da9..ad7303e66652 100644
--- a/layout/base/PresShell.cpp
+++ b/layout/base/PresShell.cpp
@@ -2200,11 +2200,10 @@ void PresShell::NotifyDestroyingFrame(nsIFrame* aFrame) {
 
     mFramesToDirty.Remove(aFrame);
 
-    nsIScrollableFrame* scrollableFrame = do_QueryFrame(aFrame);
-    if (scrollableFrame) {
-      mPendingScrollAnchorSelection.Remove(scrollableFrame);
-      mPendingScrollAnchorAdjustment.Remove(scrollableFrame);
-      mPendingScrollResnap.Remove(scrollableFrame);
+    if (ScrollContainerFrame* scrollContainerFrame = do_QueryFrame(aFrame)) {
+      mPendingScrollAnchorSelection.Remove(scrollContainerFrame);
+      mPendingScrollAnchorAdjustment.Remove(scrollContainerFrame);
+      mPendingScrollResnap.Remove(scrollContainerFrame);
     }
   }
 }
@@ -2358,7 +2357,7 @@ PresShell::ScrollPage(bool aForward) {
     scrollContainerFrame->ScrollBy(nsIntPoint(0, aForward ? 1 : -1),
                                    ScrollUnit::PAGES, scrollMode, nullptr,
                                    mozilla::ScrollOrigin::NotSpecified,
-                                   nsIScrollableFrame::NOT_MOMENTUM,
+                                   ScrollContainerFrame::NOT_MOMENTUM,
                                    ScrollSnapFlags::IntendedDirection |
                                        ScrollSnapFlags::IntendedEndPosition);
   }
@@ -2380,7 +2379,7 @@ PresShell::ScrollLine(bool aForward) {
     scrollContainerFrame->ScrollBy(
         nsIntPoint(0, aForward ? lineCount : -lineCount), ScrollUnit::LINES,
         scrollMode, nullptr, mozilla::ScrollOrigin::NotSpecified,
-        nsIScrollableFrame::NOT_MOMENTUM, ScrollSnapFlags::IntendedDirection);
+        ScrollContainerFrame::NOT_MOMENTUM, ScrollSnapFlags::IntendedDirection);
   }
   return NS_OK;
 }
@@ -2394,7 +2393,7 @@ PresShell::ScrollCharacter(bool aRight) {
     int32_t h = StaticPrefs::toolkit_scrollbox_horizontalScrollDistance();
     scrollContainerFrame->ScrollBy(
         nsIntPoint(aRight ? h : -h, 0), ScrollUnit::LINES, scrollMode, nullptr,
-        mozilla::ScrollOrigin::NotSpecified, nsIScrollableFrame::NOT_MOMENTUM,
+        mozilla::ScrollOrigin::NotSpecified, ScrollContainerFrame::NOT_MOMENTUM,
         ScrollSnapFlags::IntendedDirection);
   }
   return NS_OK;
@@ -2406,10 +2405,11 @@ PresShell::CompleteScroll(bool aForward) {
       GetScrollContainerFrameToScroll(VerticalScrollDirection);
   ScrollMode scrollMode = apz::GetScrollModeForOrigin(ScrollOrigin::Other);
   if (scrollContainerFrame) {
-    scrollContainerFrame->ScrollBy(
-        nsIntPoint(0, aForward ? 1 : -1), ScrollUnit::WHOLE, scrollMode,
-        nullptr, mozilla::ScrollOrigin::NotSpecified,
-        nsIScrollableFrame::NOT_MOMENTUM, ScrollSnapFlags::IntendedEndPosition);
+    scrollContainerFrame->ScrollBy(nsIntPoint(0, aForward ? 1 : -1),
+                                   ScrollUnit::WHOLE, scrollMode, nullptr,
+                                   mozilla::ScrollOrigin::NotSpecified,
+                                   ScrollContainerFrame::NOT_MOMENTUM,
+                                   ScrollSnapFlags::IntendedEndPosition);
   }
   return NS_OK;
 }
@@ -2581,11 +2581,11 @@ void PresShell::VerifyHasDirtyRootAncestor(nsIFrame* aFrame) {
 
 void PresShell::PostPendingScrollAnchorSelection(
     mozilla::layout::ScrollAnchorContainer* aContainer) {
-  mPendingScrollAnchorSelection.Insert(aContainer->ScrollableFrame());
+  mPendingScrollAnchorSelection.Insert(aContainer->ScrollContainer());
 }
 
 void PresShell::FlushPendingScrollAnchorSelections() {
-  for (nsIScrollableFrame* scroll : mPendingScrollAnchorSelection) {
+  for (ScrollContainerFrame* scroll : mPendingScrollAnchorSelection) {
     scroll->Anchor()->SelectAnchor();
   }
   mPendingScrollAnchorSelection.Clear();
@@ -2593,23 +2593,24 @@ void PresShell::FlushPendingScrollAnchorSelections() {
 
 void PresShell::PostPendingScrollAnchorAdjustment(
     ScrollAnchorContainer* aContainer) {
-  mPendingScrollAnchorAdjustment.Insert(aContainer->ScrollableFrame());
+  mPendingScrollAnchorAdjustment.Insert(aContainer->ScrollContainer());
 }
 
 void PresShell::FlushPendingScrollAnchorAdjustments() {
-  for (nsIScrollableFrame* scroll : mPendingScrollAnchorAdjustment) {
+  for (ScrollContainerFrame* scroll : mPendingScrollAnchorAdjustment) {
     scroll->Anchor()->ApplyAdjustments();
   }
   mPendingScrollAnchorAdjustment.Clear();
 }
 
-void PresShell::PostPendingScrollResnap(nsIScrollableFrame* aScrollableFrame) {
-  mPendingScrollResnap.Insert(aScrollableFrame);
+void PresShell::PostPendingScrollResnap(
+    ScrollContainerFrame* aScrollContainerFrame) {
+  mPendingScrollResnap.Insert(aScrollContainerFrame);
 }
 
 void PresShell::FlushPendingScrollResnap() {
-  for (nsIScrollableFrame* scrollableFrame : mPendingScrollResnap) {
-    scrollableFrame->TryResnap();
+  for (ScrollContainerFrame* scrollContainerFrame : mPendingScrollResnap) {
+    scrollContainerFrame->TryResnap();
   }
   mPendingScrollResnap.Clear();
 }
@@ -3413,18 +3414,18 @@ static nscoord ComputeWhereToScroll(WhereToScroll aWhereToScroll,
 }
 
 static WhereToScroll GetApplicableWhereToScroll(
-    const nsIScrollableFrame* aFrameAsScrollable,
+    const ScrollContainerFrame* aScrollContainerFrame,
     const nsIFrame* aScrollableFrame, const nsIFrame* aTarget,
     ScrollDirection aScrollDirection, WhereToScroll aOriginal) {
-  MOZ_ASSERT(do_QueryFrame(aFrameAsScrollable) == aScrollableFrame);
+  MOZ_ASSERT(do_QueryFrame(aScrollContainerFrame) == aScrollableFrame);
   if (aTarget == aScrollableFrame) {
     return aOriginal;
   }
 
   StyleScrollSnapAlignKeyword align =
       aScrollDirection == ScrollDirection::eHorizontal
-          ? aFrameAsScrollable->GetScrollSnapAlignFor(aTarget).first
-          : aFrameAsScrollable->GetScrollSnapAlignFor(aTarget).second;
+          ? aScrollContainerFrame->GetScrollSnapAlignFor(aTarget).first
+          : aScrollContainerFrame->GetScrollSnapAlignFor(aTarget).second;
 
   switch (align) {
     case StyleScrollSnapAlignKeyword::None:
@@ -3440,26 +3441,26 @@ static WhereToScroll GetApplicableWhereToScroll(
 }
 
 /**
- * This function takes a scrollable frame, a rect in the coordinate system
+ * This function takes a scroll container frame, a rect in the coordinate system
  * of the scrolled frame, and a desired percentage-based scroll
  * position and attempts to scroll the rect to that position in the
  * visual viewport.
  *
  * This needs to work even if aRect has a width or height of zero.
  */
-static void ScrollToShowRect(nsIScrollableFrame* aFrameAsScrollable,
+static void ScrollToShowRect(ScrollContainerFrame* aScrollContainerFrame,
                              const nsIFrame* aScrollableFrame,
                              const nsIFrame* aTarget, const nsRect& aRect,
                              const Sides aScrollPaddingSkipSides,
                              const nsMargin& aMargin, ScrollAxis aVertical,
                              ScrollAxis aHorizontal, ScrollFlags aScrollFlags) {
-  nsPoint scrollPt = aFrameAsScrollable->GetVisualViewportOffset();
+  nsPoint scrollPt = aScrollContainerFrame->GetVisualViewportOffset();
   const nsPoint originalScrollPt = scrollPt;
   const nsRect visibleRect(scrollPt,
-                           aFrameAsScrollable->GetVisualViewportSize());
+                           aScrollContainerFrame->GetVisualViewportSize());
 
   const nsMargin padding = [&] {
-    nsMargin p = aFrameAsScrollable->GetScrollPadding();
+    nsMargin p = aScrollContainerFrame->GetScrollPadding();
     p.ApplySkipSides(aScrollPaddingSkipSides);
     return p + aMargin;
   }();
@@ -3467,7 +3468,7 @@ static void ScrollToShowRect(nsIScrollableFrame* aFrameAsScrollable,
   const nsRect rectToScrollIntoView = [&] {
     nsRect r(aRect);
     r.Inflate(padding);
-    return r.Intersect(aFrameAsScrollable->GetScrolledRect());
+    return r.Intersect(aScrollContainerFrame->GetScrolledRect());
   }();
 
   nsSize lineSize;
@@ -3478,12 +3479,12 @@ static void ScrollToShowRect(nsIScrollableFrame* aFrameAsScrollable,
   // it would assert and possible give the wrong result.
   if (aVertical.mWhenToScroll == WhenToScroll::IfNotVisible ||
       aHorizontal.mWhenToScroll == WhenToScroll::IfNotVisible) {
-    lineSize = aFrameAsScrollable->GetLineScrollAmount();
+    lineSize = aScrollContainerFrame->GetLineScrollAmount();
   }
-  ScrollStyles ss = aFrameAsScrollable->GetScrollStyles();
+  ScrollStyles ss = aScrollContainerFrame->GetScrollStyles();
   nsRect allowedRange(scrollPt, nsSize(0, 0));
   ScrollDirections directions =
-      aFrameAsScrollable->GetAvailableScrollingDirections();
+      aScrollContainerFrame->GetAvailableScrollingDirections();
 
   if (((aScrollFlags & ScrollFlags::ScrollOverflowHidden) ||
        ss.mVertical != StyleOverflow::Hidden) &&
@@ -3494,7 +3495,7 @@ static void ScrollToShowRect(nsIScrollableFrame* aFrameAsScrollable,
                             visibleRect.YMost() - padding.bottom)) {
       // If the scroll-snap-align on the frame is valid, we need to respect it.
       WhereToScroll whereToScroll = GetApplicableWhereToScroll(
-          aFrameAsScrollable, aScrollableFrame, aTarget,
+          aScrollContainerFrame, aScrollableFrame, aTarget,
           ScrollDirection::eVertical, aVertical.mWhereToScroll);
 
       nscoord maxHeight;
@@ -3515,7 +3516,7 @@ static void ScrollToShowRect(nsIScrollableFrame* aFrameAsScrollable,
                             visibleRect.XMost() - padding.right)) {
       // If the scroll-snap-align on the frame is valid, we need to respect it.
       WhereToScroll whereToScroll = GetApplicableWhereToScroll(
-          aFrameAsScrollable, aScrollableFrame, aTarget,
+          aScrollContainerFrame, aScrollableFrame, aTarget,
           ScrollDirection::eHorizontal, aHorizontal.mWhereToScroll);
 
       nscoord maxWidth;
@@ -3544,17 +3545,17 @@ static void ScrollToShowRect(nsIScrollableFrame* aFrameAsScrollable,
   } else if (aScrollFlags & ScrollFlags::ScrollSmoothAuto) {
     behavior = ScrollBehavior::Auto;
   }
-  bool smoothScroll = aFrameAsScrollable->IsSmoothScroll(behavior);
+  bool smoothScroll = aScrollContainerFrame->IsSmoothScroll(behavior);
   if (smoothScroll) {
     scrollMode = ScrollMode::SmoothMsd;
   }
-  nsIFrame* frame = do_QueryFrame(aFrameAsScrollable);
+  nsIFrame* frame = do_QueryFrame(aScrollContainerFrame);
   AutoWeakFrame weakFrame(frame);
-  aFrameAsScrollable->ScrollTo(scrollPt, scrollMode, &allowedRange,
-                               ScrollSnapFlags::IntendedEndPosition,
-                               aScrollFlags & ScrollFlags::TriggeredByScript
-                                   ? ScrollTriggeredByScript::Yes
-                                   : ScrollTriggeredByScript::No);
+  aScrollContainerFrame->ScrollTo(scrollPt, scrollMode, &allowedRange,
+                                  ScrollSnapFlags::IntendedEndPosition,
+                                  aScrollFlags & ScrollFlags::TriggeredByScript
+                                      ? ScrollTriggeredByScript::Yes
+                                      : ScrollTriggeredByScript::No);
   if (!weakFrame.IsAlive()) {
     return;
   }
@@ -3563,7 +3564,7 @@ static void ScrollToShowRect(nsIScrollableFrame* aFrameAsScrollable,
   // scroll the rect into view visually, and that may require scrolling
   // the visual viewport in scenarios where there is not enough layout
   // scroll range.
-  if (aFrameAsScrollable->IsRootScrollFrameOfDocument() &&
+  if (aScrollContainerFrame->IsRootScrollFrameOfDocument() &&
       frame->PresContext()->IsRootContentDocumentCrossProcess()) {
     frame->PresShell()->ScrollToVisual(scrollPt, FrameMetrics::eMainThread,
                                        scrollMode);
@@ -3745,7 +3746,7 @@ bool PresShell::ScrollFrameIntoView(
     MaybeSkipPaddingSides(aTargetFrame);
     while (nsIFrame* parent = container->GetParent()) {
       container = parent;
-      if (static_cast<nsIScrollableFrame*>(do_QueryFrame(container))) {
+      if (container->IsScrollContainerOrSubclass()) {
         // We really just need a non-fragmented frame so that we can accumulate
         // the bounds of all our continuations relative to it. We shouldn't jump
         // out of our nearest scrollable frame, and that's an ok reference
@@ -3787,7 +3788,7 @@ bool PresShell::ScrollFrameIntoView(
   // Walk up the frame hierarchy scrolling the rect into view and
   // keeping rect relative to container
   do {
-    if (nsIScrollableFrame* sf = do_QueryFrame(container)) {
+    if (ScrollContainerFrame* sf = do_QueryFrame(container)) {
       nsPoint oldPosition = sf->GetScrollPosition();
       nsRect targetRect = rect;
       // Inflate the scrolled rect by the container's padding in each dimension,
@@ -6013,8 +6014,7 @@ void PresShell::MarkFramesInSubtreeApproximatelyVisible(
 
   nsRect rect = aRect;
 
-  nsIScrollableFrame* scrollFrame = do_QueryFrame(aFrame);
-  if (scrollFrame) {
+  if (ScrollContainerFrame* scrollFrame = do_QueryFrame(aFrame)) {
     bool ignoreDisplayPort = false;
     if (DisplayPortUtils::IsMissingDisplayPortBaseRect(aFrame->GetContent())) {
       // We can properly set the base rect for root scroll frames on top level
@@ -8079,7 +8079,7 @@ PresShell::EventHandler::ComputeRootFrameToHandleEventWithCapturingContent(
 
   // scrollable frames should use the scrolling container as the root instead
   // of the document
-  nsIScrollableFrame* scrollFrame = do_QueryFrame(captureFrame);
+  ScrollContainerFrame* scrollFrame = do_QueryFrame(captureFrame);
   return scrollFrame ? scrollFrame->GetScrolledFrame()
                      : aRootFrameToHandleEvent;
 }
diff --git a/layout/base/PresShell.h b/layout/base/PresShell.h
index 303ad727ad48..1f710a5897b6 100644
--- a/layout/base/PresShell.h
+++ b/layout/base/PresShell.h
@@ -68,7 +68,6 @@ class nsIFrame;
 class nsILayoutHistoryState;
 class nsINode;
 class nsIReflowCallback;
-class nsIScrollableFrame;
 class nsITimer;
 class nsPageSequenceFrame;
 class nsPIDOMWindowOuter;
@@ -485,7 +484,7 @@ class PresShell final : public nsStubDocumentObserver,
   void PostPendingScrollAnchorAdjustment(
       layout::ScrollAnchorContainer* aContainer);
 
-  void PostPendingScrollResnap(nsIScrollableFrame* aScrollableFrame);
+  void PostPendingScrollResnap(ScrollContainerFrame* aScrollContainerFrame);
   void FlushPendingScrollResnap();
 
   void CancelAllPendingReflows();
@@ -1198,7 +1197,7 @@ class PresShell final : public nsStubDocumentObserver,
   // content (such as via window.scrollTo() should scroll the layout viewport
   // only).
   // If scrolling "far away", i.e. not just within the existing layout
-  // viewport, it's recommended to use both nsIScrollableFrame.ScrollTo*()
+  // viewport, it's recommended to use both ScrollContainerFrame.ScrollTo*()
   // (via window.scrollTo if calling from JS) *and* this function; otherwise,
   // temporary checkerboarding may result. If doing this:
   //   * Be sure to call ScrollTo*() first, as a subsequent layout scroll
@@ -1286,7 +1285,7 @@ class PresShell final : public nsStubDocumentObserver,
    * |aOrigin| specifies who originated the resolution change. For changes
    * sent by APZ, pass ResolutionChangeOrigin::Apz. For changes sent by
    * the main thread, pass ResolutionChangeOrigin::MainThreadAdjustment (similar
-   * to the |aOrigin| parameter of nsIScrollableFrame::ScrollToCSSPixels()).
+   * to the |aOrigin| parameter of ScrollContainerFrame::ScrollToCSSPixels()).
    */
   nsresult SetResolutionAndScaleTo(float aResolution,
                                    ResolutionChangeOrigin aOrigin);
@@ -1642,14 +1641,14 @@ class PresShell final : public nsStubDocumentObserver,
    *                      iframe or the like.  If ScrollFlags::ScrollSmooth
    *                      is set and CSSOM-VIEW scroll-behavior is enabled,
    *                      we will scroll smoothly using
-   *                      nsIScrollableFrame::ScrollMode::SMOOTH_MSD;
-   *                      otherwise, nsIScrollableFrame::ScrollMode::INSTANT
+   *                      ScrollContainerFrame::ScrollMode::SMOOTH_MSD;
+   *                      otherwise, ScrollContainerFrame::ScrollMode::INSTANT
    *                      will be used.  If ScrollFlags::ScrollSmoothAuto is
    *                      set, the CSSOM-View scroll-behavior attribute is
    *                      set to 'smooth' on the scroll frame, and CSSOM-VIEW
    *                      scroll-behavior is enabled, we will scroll smoothly
-   *                      using nsIScrollableFrame::ScrollMode::SMOOTH_MSD;
-   *                      otherwise, nsIScrollableFrame::ScrollMode::INSTANT
+   *                      using ScrollContainerFrame::ScrollMode::SMOOTH_MSD;
+   *                      otherwise, ScrollContainerFrame::ScrollMode::INSTANT
    *                      will be used.
    */
   MOZ_CAN_RUN_SCRIPT
@@ -3014,9 +3013,9 @@ class PresShell final : public nsStubDocumentObserver,
   // Set of frames that we should mark with NS_FRAME_HAS_DIRTY_CHILDREN after
   // we finish reflowing mCurrentReflowRoot.
   nsTHashSet<nsIFrame*> mFramesToDirty;
-  nsTHashSet<nsIScrollableFrame*> mPendingScrollAnchorSelection;
-  nsTHashSet<nsIScrollableFrame*> mPendingScrollAnchorAdjustment;
-  nsTHashSet<nsIScrollableFrame*> mPendingScrollResnap;
+  nsTHashSet<ScrollContainerFrame*> mPendingScrollAnchorSelection;
+  nsTHashSet<ScrollContainerFrame*> mPendingScrollAnchorAdjustment;
+  nsTHashSet<ScrollContainerFrame*> mPendingScrollResnap;
 
   nsTHashSet<nsIContent*> mHiddenContentInForcedLayout;
 
diff --git a/layout/base/RestyleManager.cpp b/layout/base/RestyleManager.cpp
index cf94d36d60db..337600dfdb92 100644
--- a/layout/base/RestyleManager.cpp
+++ b/layout/base/RestyleManager.cpp
@@ -39,7 +39,6 @@
 #include "ScrollSnap.h"
 #include "nsAnimationManager.h"
 #include "nsBlockFrame.h"
-#include "nsIScrollableFrame.h"
 #include "nsContentUtils.h"
 #include "nsCSSFrameConstructor.h"
 #include "nsCSSRendering.h"
@@ -1459,7 +1458,7 @@ static inline void TryToDealWithScrollbarChange(nsChangeHint& aHint,
         // Under these conditions, we're OK to assume that this "overflow"
         // change only impacts the root viewport's scrollframe, which
         // already exists, so we can simply reflow instead of reframing.
-        if (nsIScrollableFrame* sf = do_QueryFrame(aFrame)) {
+        if (ScrollContainerFrame* sf = do_QueryFrame(aFrame)) {
           sf->MarkScrollbarsDirtyForReflow();
         } else if (ScrollContainerFrame* sf =
                        aPc->PresShell()->GetRootScrollContainerFrame()) {
@@ -1476,7 +1475,7 @@ static inline void TryToDealWithScrollbarChange(nsChangeHint& aHint,
   }
 
   const bool scrollable = aFrame->StyleDisplay()->IsScrollableOverflow();
-  if (nsIScrollableFrame* sf = do_QueryFrame(aFrame)) {
+  if (ScrollContainerFrame* sf = do_QueryFrame(aFrame)) {
     if (scrollable && sf->HasAllNeededScrollbars()) {
       sf->MarkScrollbarsDirtyForReflow();
       // Once we've created scrollbars for a frame, don't bother reconstructing
diff --git a/layout/base/ScrollTypes.h b/layout/base/ScrollTypes.h
index 512c2579bce9..e2aff6f61f39 100644
--- a/layout/base/ScrollTypes.h
+++ b/layout/base/ScrollTypes.h
@@ -7,13 +7,13 @@
 
 #include "mozilla/TypedEnumBits.h"
 
-// Types used in main-thread scrolling interfaces such as nsIScrollableFrame.
+// Types used in main-thread scrolling interfaces such as ScrollContainerFrame.
 
 namespace mozilla {
 
 /**
  * Scroll modes for main-thread scroll operations. These are mostly used
- * by nsIScrollableFrame methods.
+ * by ScrollContainerFrame methods.
  *
  * When a scroll operation is requested, we ask for instant, smooth,
  * smooth msd, or normal scrolling.
diff --git a/layout/base/ViewportUtils.cpp b/layout/base/ViewportUtils.cpp
index a5869bdcbf43..0e2bcb891f98 100644
--- a/layout/base/ViewportUtils.cpp
+++ b/layout/base/ViewportUtils.cpp
@@ -244,7 +244,7 @@ const nsIFrame* ViewportUtils::IsZoomedContentRoot(const nsIFrame* aFrame) {
   }
   if (aFrame->Type() == LayoutFrameType::Canvas ||
       aFrame->Type() == LayoutFrameType::PageSequence) {
-    nsIScrollableFrame* sf = do_QueryFrame(aFrame->GetParent());
+    ScrollContainerFrame* sf = do_QueryFrame(aFrame->GetParent());
     if (sf && sf->IsRootScrollFrameOfDocument() &&
         aFrame->PresContext()->IsRootContentDocumentCrossProcess()) {
       return aFrame->GetParent();
diff --git a/layout/base/nsCSSFrameConstructor.cpp b/layout/base/nsCSSFrameConstructor.cpp
index 0eb3ec14cb09..e294f80d1ec0 100644
--- a/layout/base/nsCSSFrameConstructor.cpp
+++ b/layout/base/nsCSSFrameConstructor.cpp
@@ -77,7 +77,6 @@
 #include "nsIObjectLoadingContent.h"
 #include "nsIPopupContainer.h"
 #include "nsIScriptError.h"
-#include "nsIScrollableFrame.h"
 #include "nsLayoutUtils.h"
 #include "nsListControlFrame.h"
 #include "nsMathMLParts.h"
@@ -5477,8 +5476,9 @@ nsContainerFrame* nsCSSFrameConstructor::GetAbsoluteContainingBlock(
       type = absPosCBCandidate->Type();
     }
     if (type == LayoutFrameType::ScrollContainer) {
-      nsIScrollableFrame* scrollFrame = do_QueryFrame(absPosCBCandidate);
-      absPosCBCandidate = scrollFrame->GetScrolledFrame();
+      ScrollContainerFrame* scrollContainerFrame =
+          do_QueryFrame(absPosCBCandidate);
+      absPosCBCandidate = scrollContainerFrame->GetScrolledFrame();
       if (!absPosCBCandidate) {
         continue;
       }
diff --git a/layout/base/nsCaret.cpp b/layout/base/nsCaret.cpp
index 8707dcba5f15..775d72845e01 100644
--- a/layout/base/nsCaret.cpp
+++ b/layout/base/nsCaret.cpp
@@ -14,13 +14,13 @@
 #include "mozilla/CaretAssociationHint.h"
 #include "mozilla/gfx/2D.h"
 #include "mozilla/intl/BidiEmbeddingLevel.h"
+#include "mozilla/ScrollContainerFrame.h"
 #include "mozilla/StaticPrefs_bidi.h"
 #include "nsCOMPtr.h"
 #include "nsFontMetrics.h"
 #include "nsITimer.h"
 #include "nsFrameSelection.h"
 #include "nsIFrame.h"
-#include "nsIScrollableFrame.h"
 #include "nsIContent.h"
 #include "nsIFrameInlines.h"
 #include "nsLayoutUtils.h"
@@ -188,7 +188,7 @@ void nsCaret::SetCaretReadOnly(bool aReadOnly) {
 static nsPoint AdjustRectForClipping(const nsRect& aRect, nsIFrame* aFrame,
                                      bool aVertical) {
   nsRect rectRelativeToClip = aRect;
-  nsIScrollableFrame* sf = nullptr;
+  ScrollContainerFrame* sf = nullptr;
   nsIFrame* scrollFrame = nullptr;
   for (nsIFrame* current = aFrame; current; current = current->GetParent()) {
     if ((sf = do_QueryFrame(current))) {
diff --git a/layout/base/nsDocumentViewer.cpp b/layout/base/nsDocumentViewer.cpp
index cea0832f2cff..3bc57a037715 100644
--- a/layout/base/nsDocumentViewer.cpp
+++ b/layout/base/nsDocumentViewer.cpp
@@ -2963,7 +2963,7 @@ static nscoord ScrollPositionForFrame(
     const nsIFrame* aFrame, ScrollContainerFrame* aScrollContainerFrame,
     float aPreviewScale) {
   // Note that even if the computed scroll position is out of the range of
-  // the scroll port, it gets clamped in nsIScrollableFrame::ScrollTo.
+  // the scroll port, it gets clamped in ScrollContainerFrame::ScrollTo.
   return nscoord(aPreviewScale * aFrame->GetRect().Center().y -
                  float(aScrollContainerFrame->GetScrollPortRect().height) /
                      2.0f);
diff --git a/layout/base/nsLayoutUtils.cpp b/layout/base/nsLayoutUtils.cpp
index 24d65a184544..d49896183e66 100644
--- a/layout/base/nsLayoutUtils.cpp
+++ b/layout/base/nsLayoutUtils.cpp
@@ -781,13 +781,11 @@ bool nsLayoutUtils::ShouldDisableApzForElement(nsIContent* aContent) {
 }
 
 void nsLayoutUtils::NotifyPaintSkipTransaction(ViewID aScrollId) {
-  if (nsIScrollableFrame* scrollFrame =
+  if (ScrollContainerFrame* sf =
           nsLayoutUtils::FindScrollContainerFrameFor(aScrollId)) {
-#ifdef DEBUG
-    nsIFrame* f = do_QueryFrame(scrollFrame);
-    MOZ_ASSERT(f && f->PresShell() && !f->PresShell()->IsResolutionUpdated());
-#endif
-    scrollFrame->NotifyApzTransaction();
+    MOZ_ASSERT(sf && sf->PresShell() &&
+               !sf->PresShell()->IsResolutionUpdated());
+    sf->NotifyApzTransaction();
   }
 }
 
@@ -1332,13 +1330,13 @@ static nsIFrame* GetNearestScrollableOrOverflowClipFrame(
     if ((aFlags & nsLayoutUtils::SCROLLABLE_STOP_AT_PAGE) && f->IsPageFrame()) {
       break;
     }
-    if (nsIScrollableFrame* scrollableFrame = do_QueryFrame(f)) {
+    if (ScrollContainerFrame* scrollContainerFrame = do_QueryFrame(f)) {
       if (aFlags & nsLayoutUtils::SCROLLABLE_ONLY_ASYNC_SCROLLABLE) {
-        if (scrollableFrame->WantAsyncScroll()) {
+        if (scrollContainerFrame->WantAsyncScroll()) {
           return f;
         }
       } else {
-        ScrollStyles ss = scrollableFrame->GetScrollStyles();
+        ScrollStyles ss = scrollContainerFrame->GetScrollStyles();
         if ((aFlags & nsLayoutUtils::SCROLLABLE_INCLUDE_HIDDEN) ||
             ss.mVertical != StyleOverflow::Hidden ||
             ss.mHorizontal != StyleOverflow::Hidden) {
@@ -2379,7 +2377,7 @@ nsRect nsLayoutUtils::ClampRectToScrollFrames(nsIFrame* aFrame,
   nsRect resultRect = aRect;
 
   while (closestScrollFrame) {
-    nsIScrollableFrame* sf = do_QueryFrame(closestScrollFrame);
+    ScrollContainerFrame* sf = do_QueryFrame(closestScrollFrame);
 
     nsRect scrollPortRect = sf->GetScrollPortRect();
     nsLayoutUtils::TransformRect(closestScrollFrame, aFrame, scrollPortRect);
@@ -5732,8 +5730,7 @@ bool nsLayoutUtils::GetFirstLinePosition(WritingMode aWM,
     }
 
     // For first-line baselines, we have to consider scroll frames.
-    if (nsIScrollableFrame* sFrame =
-            do_QueryFrame(const_cast<nsIFrame*>(aFrame))) {
+    if (const ScrollContainerFrame* sFrame = do_QueryFrame(aFrame)) {
       LinePosition kidPosition;
       if (GetFirstLinePosition(aWM, sFrame->GetScrolledFrame(), &kidPosition)) {
         // Consider only the border (Padding is ignored, since
@@ -5826,7 +5823,7 @@ bool nsLayoutUtils::GetLastLineBaseline(WritingMode aWM, const nsIFrame* aFrame,
 
   const nsBlockFrame* block = do_QueryFrame(aFrame);
   if (!block) {
-    if (nsIScrollableFrame* sFrame = do_QueryFrame(aFrame)) {
+    if (const ScrollContainerFrame* sFrame = do_QueryFrame(aFrame)) {
       // Use the baseline position only if the last line's baseline is within
       // the scrolling frame's box in the initial position.
       const auto* scrolledFrame = sFrame->GetScrolledFrame();
@@ -8327,7 +8324,7 @@ nsMargin nsLayoutUtils::ScrollbarAreaToExcludeFromCompositionBoundsFor(
     return nsMargin();
   }
   return scrollContainerFrame->GetActualScrollbarSizes(
-      nsIScrollableFrame::ScrollbarSizesOptions::
+      ScrollContainerFrame::ScrollbarSizesOptions::
           INCLUDE_VISUAL_VIEWPORT_SCROLLBARS);
 }
 
diff --git a/layout/forms/nsComboboxControlFrame.cpp b/layout/forms/nsComboboxControlFrame.cpp
index 98486255d09c..6b4ce653e10e 100644
--- a/layout/forms/nsComboboxControlFrame.cpp
+++ b/layout/forms/nsComboboxControlFrame.cpp
@@ -24,7 +24,6 @@
 #include "mozilla/dom/Event.h"
 #include "mozilla/dom/HTMLSelectElement.h"
 #include "mozilla/dom/Document.h"
-#include "nsIScrollableFrame.h"
 #include "mozilla/ServoStyleSet.h"
 #include "nsNodeInfoManager.h"
 #include "nsContentCreatorFunctions.h"
diff --git a/layout/forms/nsListControlFrame.cpp b/layout/forms/nsListControlFrame.cpp
index 9740b04bf1e2..6bebfaa8f16b 100644
--- a/layout/forms/nsListControlFrame.cpp
+++ b/layout/forms/nsListControlFrame.cpp
@@ -12,7 +12,6 @@
 #include "nsGkAtoms.h"
 #include "nsComboboxControlFrame.h"
 #include "nsFontMetrics.h"
-#include "nsIScrollableFrame.h"
 #include "nsCSSRendering.h"
 #include "nsLayoutUtils.h"
 #include "nsDisplayList.h"
diff --git a/layout/forms/nsTextControlFrame.cpp b/layout/forms/nsTextControlFrame.cpp
index 75b7ce68b69b..91dba2043f74 100644
--- a/layout/forms/nsTextControlFrame.cpp
+++ b/layout/forms/nsTextControlFrame.cpp
@@ -225,11 +225,11 @@ LogicalSize nsTextControlFrame::CalcIntrinsicSize(gfxContext* aRenderingContext,
 
   // Add in the size of the scrollbars for textarea
   if (IsTextArea()) {
-    nsIScrollableFrame* scrollableFrame = GetScrollTargetFrame();
-    NS_ASSERTION(scrollableFrame, "Child must be scrollable");
-    if (scrollableFrame) {
-      LogicalMargin scrollbarSizes(aWM,
-                                   scrollableFrame->GetDesiredScrollbarSizes());
+    ScrollContainerFrame* scrollContainerFrame = GetScrollTargetFrame();
+    NS_ASSERTION(scrollContainerFrame, "Child must be scrollable");
+    if (scrollContainerFrame) {
+      LogicalMargin scrollbarSizes(
+          aWM, scrollContainerFrame->GetDesiredScrollbarSizes());
       intrinsicSize.ISize(aWM) += scrollbarSizes.IStartEnd(aWM);
 
       // We only include scrollbar-thickness in our BSize if the scrollbar on
diff --git a/layout/generic/ReflowInput.h b/layout/generic/ReflowInput.h
index 7bf7c4fc7358..9ff903ecbd79 100644
--- a/layout/generic/ReflowInput.h
+++ b/layout/generic/ReflowInput.h
@@ -460,11 +460,11 @@ struct ReflowInput : public SizeComputationInput {
     // infinite loops.
     bool mIsTopOfPage : 1;
 
-    // parent frame is an nsIScrollableFrame and it is assuming a horizontal
+    // parent frame is an ScrollContainerFrame and it is assuming a horizontal
     // scrollbar
     bool mAssumingHScrollbar : 1;
 
-    // parent frame is an nsIScrollableFrame and it is assuming a vertical
+    // parent frame is an ScrollContainerFrame and it is assuming a vertical
     // scrollbar
     bool mAssumingVScrollbar : 1;
 
diff --git a/layout/generic/ScrollAnchorContainer.cpp b/layout/generic/ScrollAnchorContainer.cpp
index 1755b38b941d..938624f7f995 100644
--- a/layout/generic/ScrollAnchorContainer.cpp
+++ b/layout/generic/ScrollAnchorContainer.cpp
@@ -75,7 +75,7 @@ ScrollAnchorContainer* ScrollAnchorContainer::FindFor(nsIFrame* aFrame) {
   return nullptr;
 }
 
-nsIScrollableFrame* ScrollAnchorContainer::ScrollableFrame() const {
+ScrollContainerFrame* ScrollAnchorContainer::ScrollContainer() const {
   return Frame()->GetScrollTargetFrame();
 }
 
@@ -314,7 +314,7 @@ void ScrollAnchorContainer::UserScrolled() {
   if (!StaticPrefs::
           layout_css_scroll_anchoring_reset_heuristic_during_animation() &&
       Frame()->ScrollAnimationState().contains(
-          nsIScrollableFrame::AnimationState::APZInProgress)) {
+          ScrollContainerFrame::AnimationState::APZInProgress)) {
     // We'd want to skip resetting our heuristic while APZ is running an async
     // scroll because this UserScrolled function gets called on every refresh
     // driver's tick during running the async scroll, thus it will clobber the
@@ -465,7 +465,7 @@ void ScrollAnchorContainer::ApplyAdjustments() {
            layout_css_scroll_anchoring_reset_heuristic_during_animation() &&
        Frame()->IsProcessingScrollEvent()) ||
       Frame()->ScrollAnimationState().contains(
-          nsIScrollableFrame::AnimationState::TriggeredByScript) ||
+          ScrollContainerFrame::AnimationState::TriggeredByScript) ||
       Frame()->GetScrollPosition() == nsPoint()) {
     ANCHOR_LOG(
         "Ignoring post-reflow (anchor=%p, dirty=%d, disabled=%d, "
@@ -476,7 +476,7 @@ void ScrollAnchorContainer::ApplyAdjustments() {
         Frame()->HasPendingScrollRestoration(),
         Frame()->IsProcessingScrollEvent(),
         Frame()->ScrollAnimationState().contains(
-            nsIScrollableFrame::AnimationState::TriggeredByScript),
+            ScrollContainerFrame::AnimationState::TriggeredByScript),
         Frame()->GetScrollPosition() == nsPoint(), mSuppressAnchorAdjustment,
         this);
     if (mSuppressAnchorAdjustment) {
@@ -610,11 +610,11 @@ ScrollAnchorContainer::ExamineAnchorCandidate(nsIFrame* aFrame) const {
 
   // See if this frame has or could maintain its own anchor node.
   const bool isScrollableWithAnchor = [&] {
-    nsIScrollableFrame* scrollable = do_QueryFrame(aFrame);
-    if (!scrollable) {
+    ScrollContainerFrame* scrollContainer = do_QueryFrame(aFrame);
+    if (!scrollContainer) {
       return false;
     }
-    auto* anchor = scrollable->Anchor();
+    auto* anchor = scrollContainer->Anchor();
     return anchor->AnchorNode() || anchor->CanMaintainAnchor();
   }();
 
diff --git a/layout/generic/ScrollAnchorContainer.h b/layout/generic/ScrollAnchorContainer.h
index 1b919fe2a72d..fadcffe4c896 100644
--- a/layout/generic/ScrollAnchorContainer.h
+++ b/layout/generic/ScrollAnchorContainer.h
@@ -13,7 +13,6 @@
 
 class nsFrameList;
 class nsIFrame;
-class nsIScrollableFrame;
 
 namespace mozilla {
 class ScrollContainerFrame;
@@ -22,8 +21,8 @@ class ScrollContainerFrame;
 namespace mozilla::layout {
 
 /**
- * A scroll anchor container finds a descendent element of a scrollable frame
- * to be an anchor node. After every reflow, the scroll anchor will apply
+ * A scroll anchor container finds a descendent element of a scroll container
+ * frame to be an anchor node. After every reflow, the scroll anchor will apply
  * scroll adjustments to keep the anchor node in the same relative position.
  *
  * See: https://drafts.csswg.org/css-scroll-anchoring/
@@ -49,14 +48,15 @@ class ScrollAnchorContainer final {
   ScrollContainerFrame* Frame() const;
 
   /**
-   * Returns the frame that owns this scroll anchor container as a scrollable
-   * frame. This is always non-null.
+   * Returns the scroll container frame that owns this scroll anchor container.
+   * This is always non-null.
    */
-  nsIScrollableFrame* ScrollableFrame() const;
+  ScrollContainerFrame* ScrollContainer() const;
 
   /**
-   * Find a suitable anchor node among the descendants of the scrollable frame.
-   * This should only be called after the scroll anchor has been invalidated.
+   * Find a suitable anchor node among the descendants of the scroll container
+   * frame. This should only be called after the scroll anchor has been
+   * invalidated.
    */
   void SelectAnchor();
 
diff --git a/layout/generic/ScrollContainerFrame.cpp b/layout/generic/ScrollContainerFrame.cpp
index 897385c3cc7f..3d346266cff8 100644
--- a/layout/generic/ScrollContainerFrame.cpp
+++ b/layout/generic/ScrollContainerFrame.cpp
@@ -1729,7 +1729,7 @@ void ScrollContainerFrame::HandleScrollbarStyleSwitching() {
     mScrollbarActivity->Destroy();
     mScrollbarActivity = nullptr;
   } else if (!mScrollbarActivity && UsesOverlayScrollbars()) {
-    mScrollbarActivity = new ScrollbarActivity(do_QueryFrame(this));
+    mScrollbarActivity = new ScrollbarActivity(this);
   }
 }
 
@@ -1877,7 +1877,7 @@ void ScrollContainerFrame::ScrollByLine(nsScrollbarFrame* aScrollbar,
 
   nsIntPoint overflow;
   ScrollBy(delta, ScrollUnit::LINES, ScrollMode::Smooth, &overflow,
-           ScrollOrigin::Other, nsIScrollableFrame::NOT_MOMENTUM, aSnapFlags);
+           ScrollOrigin::Other, NOT_MOMENTUM, aSnapFlags);
 }
 
 void ScrollContainerFrame::RepeatButtonScroll(nsScrollbarFrame* aScrollbar) {
@@ -1932,8 +1932,8 @@ void ScrollContainerFrame::ScrollByUnit(nsScrollbarFrame* aScrollbar,
     delta.y = aDirection;
   }
   nsIntPoint overflow;
-  ScrollBy(delta, aUnit, aMode, &overflow, ScrollOrigin::Other,
-           nsIScrollableFrame::NOT_MOMENTUM, aSnapFlags);
+  ScrollBy(delta, aUnit, aMode, &overflow, ScrollOrigin::Other, NOT_MOMENTUM,
+           aSnapFlags);
 }
 
 //-------------------- Helper ----------------------
@@ -4805,20 +4805,21 @@ static void CalcRangeForScrollBy(int32_t aDelta, nscoord aPos,
                                   (aDelta > 0 ? aPosTolerance : aNegTolerance));
 }
 
-void ScrollContainerFrame::ScrollBy(
-    nsIntPoint aDelta, ScrollUnit aUnit, ScrollMode aMode,
-    nsIntPoint* aOverflow, ScrollOrigin aOrigin,
-    nsIScrollableFrame::ScrollMomentum aMomentum, ScrollSnapFlags aSnapFlags) {
+void ScrollContainerFrame::ScrollBy(nsIntPoint aDelta, ScrollUnit aUnit,
+                                    ScrollMode aMode, nsIntPoint* aOverflow,
+                                    ScrollOrigin aOrigin,
+                                    ScrollMomentum aMomentum,
+                                    ScrollSnapFlags aSnapFlags) {
   // When a smooth scroll is being processed on a frame, mouse wheel and
   // trackpad momentum scroll event updates must notcancel the SMOOTH or
   // SMOOTH_MSD scroll animations, enabling Javascript that depends on them to
   // be responsive without forcing the user to wait for the fling animations to
   // completely stop.
   switch (aMomentum) {
-    case nsIScrollableFrame::NOT_MOMENTUM:
+    case NOT_MOMENTUM:
       mIgnoreMomentumScroll = false;
       break;
-    case nsIScrollableFrame::SYNTHESIZED_MOMENTUM_EVENT:
+    case SYNTHESIZED_MOMENTUM_EVENT:
       if (mIgnoreMomentumScroll) {
         return;
       }
@@ -6962,16 +6963,13 @@ nsRect ScrollContainerFrame::GetUnsnappedScrolledRectInternal(
 }
 
 nsMargin ScrollContainerFrame::GetActualScrollbarSizes(
-    nsIScrollableFrame::ScrollbarSizesOptions
-        aOptions /* = nsIScrollableFrame::ScrollbarSizesOptions::NONE */)
-    const {
+    ScrollbarSizesOptions aOptions /* = ScrollbarSizesOptions::NONE */) const {
   nsRect r = GetPaddingRectRelativeToSelf();
 
   nsMargin m(mScrollPort.y - r.y, r.XMost() - mScrollPort.XMost(),
              r.YMost() - mScrollPort.YMost(), mScrollPort.x - r.x);
 
-  if (aOptions == nsIScrollableFrame::ScrollbarSizesOptions::
-                      INCLUDE_VISUAL_VIEWPORT_SCROLLBARS &&
+  if (aOptions == ScrollbarSizesOptions::INCLUDE_VISUAL_VIEWPORT_SCROLLBARS &&
       !UsesOverlayScrollbars()) {
     // If we are using layout scrollbars and they only exist to scroll the
     // visual viewport then they do not take up any layout space (so the
@@ -7066,8 +7064,8 @@ bool ScrollContainerFrame::IsLastScrollUpdateTriggeredByScriptAnimating()
   return false;
 }
 
-using AnimationState = nsIScrollableFrame::AnimationState;
-EnumSet<AnimationState> ScrollContainerFrame::ScrollAnimationState() const {
+EnumSet<ScrollContainerFrame::AnimationState>
+ScrollContainerFrame::ScrollAnimationState() const {
   EnumSet<AnimationState> retval;
   if (IsApzAnimationInProgress()) {
     retval += AnimationState::APZInProgress;
@@ -7471,7 +7469,7 @@ static void CollectScrollPositionsForSnap(
     ScrollContainerFrame::SnapTargetSet* aSnapTargets) {
   // Snap positions only affect the nearest ancestor scroll container on the
   // element's containing block chain.
-  nsIScrollableFrame* sf = do_QueryFrame(aFrame);
+  ScrollContainerFrame* sf = do_QueryFrame(aFrame);
   if (sf) {
     return;
   }
@@ -8009,7 +8007,7 @@ void ScrollContainerFrame::AppendScrollUpdate(
 void ScrollContainerFrame::ScheduleScrollAnimations() {
   nsIContent* content = GetContent();
   MOZ_ASSERT(content && content->IsElement(),
-             "The nsIScrollableFrame should have the element.");
+             "The ScrollContainerFrame should have the element.");
 
   const Element* elementOrPseudo = content->AsElement();
   PseudoStyleType pseudo = elementOrPseudo->GetPseudoElementType();
diff --git a/layout/generic/ScrollContainerFrame.h b/layout/generic/ScrollContainerFrame.h
index f7b57f40fced..b82ae542cac6 100644
--- a/layout/generic/ScrollContainerFrame.h
+++ b/layout/generic/ScrollContainerFrame.h
@@ -70,7 +70,6 @@ class ScrollContainerFrame : public nsContainerFrame,
                              public nsIStatefulFrame {
  public:
   using Element = dom::Element;
-  using InScrollingGesture = nsIScrollableFrame::InScrollingGesture;
   using ScrollAnchorContainer = layout::ScrollAnchorContainer;
   using SnapTargetSet = nsTHashSet<RefPtr<nsIContent>>;
 
@@ -203,8 +202,7 @@ class ScrollContainerFrame : public nsContainerFrame,
     return result;
   }
   nsMargin GetActualScrollbarSizes(
-      nsIScrollableFrame::ScrollbarSizesOptions aOptions =
-          nsIScrollableFrame::ScrollbarSizesOptions::NONE) const final;
+      ScrollbarSizesOptions aOptions = ScrollbarSizesOptions::NONE) const final;
   nsMargin GetDesiredScrollbarSizes() const final;
   static nscoord GetNonOverlayScrollbarSize(const nsPresContext*,
                                             StyleScrollbarWidth);
@@ -266,8 +264,7 @@ class ScrollContainerFrame : public nsContainerFrame,
   void ScrollBy(nsIntPoint aDelta, ScrollUnit aUnit, ScrollMode aMode,
                 nsIntPoint* aOverflow = nullptr,
                 ScrollOrigin aOrigin = ScrollOrigin::NotSpecified,
-                nsIScrollableFrame::ScrollMomentum aMomentum =
-                    nsIScrollableFrame::NOT_MOMENTUM,
+                ScrollMomentum aMomentum = NOT_MOMENTUM,
                 ScrollSnapFlags aSnapFlags = ScrollSnapFlags::Disabled) final;
   void ScrollByCSSPixels(const CSSIntPoint& aDelta,
                          ScrollMode aMode = ScrollMode::Instant) final {
@@ -310,7 +307,6 @@ class ScrollContainerFrame : public nsContainerFrame,
   bool IsRectNearlyVisible(const nsRect& aRect) const final;
   nsRect ExpandRectToNearlyVisible(const nsRect& aRect) const final;
   ScrollOrigin LastScrollOrigin() const final { return mLastScrollOrigin; }
-  using AnimationState = nsIScrollableFrame::AnimationState;
   EnumSet<AnimationState> ScrollAnimationState() const final;
   MainThreadScrollGeneration CurrentScrollGeneration() const final {
     return mScrollGeneration;
@@ -392,7 +388,6 @@ class ScrollContainerFrame : public nsContainerFrame,
   void TryResnap() final;
   void PostPendingResnapIfNeeded(const nsIFrame* aFrame) final;
   void PostPendingResnap() final;
-  using PhysicalScrollSnapAlign = nsIScrollableFrame::PhysicalScrollSnapAlign;
   PhysicalScrollSnapAlign GetScrollSnapAlignFor(
       const nsIFrame* aFrame) const final;
 
diff --git a/layout/generic/ScrollbarActivity.cpp b/layout/generic/ScrollbarActivity.cpp
index e9865c62f929..d7c16d19ffb8 100644
--- a/layout/generic/ScrollbarActivity.cpp
+++ b/layout/generic/ScrollbarActivity.cpp
@@ -11,7 +11,6 @@
 #include "nsContentUtils.h"
 #include "nsITimer.h"
 #include "nsQueryFrame.h"
-#include "nsIScrollableFrame.h"
 #include "PresShell.h"
 #include "nsLayoutUtils.h"
 #include "nsScrollbarFrame.h"
@@ -20,6 +19,7 @@
 #include "mozilla/dom/Event.h"
 #include "mozilla/dom/Document.h"
 #include "mozilla/LookAndFeel.h"
+#include "mozilla/ScrollContainerFrame.h"
 
 namespace mozilla::layout {
 
@@ -100,12 +100,14 @@ ScrollbarActivity::HandleEvent(dom::Event* aEvent) {
     // of our scroll frame) and we don't want those to activate us.
     nsIFrame* scrollFrame = do_QueryFrame(mScrollableFrame);
     MOZ_ASSERT(scrollFrame);
-    nsIScrollableFrame* scrollableFrame = do_QueryFrame(mScrollableFrame);
+    ScrollContainerFrame* scrollContainerFrame =
+        do_QueryFrame(mScrollableFrame);
     nsCOMPtr<nsIContent> targetContent =
         do_QueryInterface(aEvent->GetOriginalTarget());
     nsIFrame* targetFrame =
         targetContent ? targetContent->GetPrimaryFrame() : nullptr;
-    if ((scrollableFrame && scrollableFrame->IsRootScrollFrameOfDocument()) ||
+    if ((scrollContainerFrame &&
+         scrollContainerFrame->IsRootScrollFrameOfDocument()) ||
         !targetFrame ||
         nsLayoutUtils::IsAncestorFrameCrossDocInProcess(
             scrollFrame, targetFrame,
diff --git a/layout/generic/StickyScrollContainer.cpp b/layout/generic/StickyScrollContainer.cpp
index 0c5fc3420217..cd0a36b12d0d 100644
--- a/layout/generic/StickyScrollContainer.cpp
+++ b/layout/generic/StickyScrollContainer.cpp
@@ -15,7 +15,6 @@
 #include "mozilla/ScrollContainerFrame.h"
 #include "nsIFrame.h"
 #include "nsIFrameInlines.h"
-#include "nsIScrollableFrame.h"
 #include "nsLayoutUtils.h"
 
 namespace mozilla {
@@ -23,13 +22,14 @@ namespace mozilla {
 NS_DECLARE_FRAME_PROPERTY_DELETABLE(StickyScrollContainerProperty,
                                     StickyScrollContainer)
 
-StickyScrollContainer::StickyScrollContainer(nsIScrollableFrame* aScrollFrame)
-    : mScrollFrame(aScrollFrame) {
-  mScrollFrame->AddScrollPositionListener(this);
+StickyScrollContainer::StickyScrollContainer(
+    ScrollContainerFrame* aScrollContainerFrame)
+    : mScrollContainerFrame(aScrollContainerFrame) {
+  mScrollContainerFrame->AddScrollPositionListener(this);
 }
 
 StickyScrollContainer::~StickyScrollContainer() {
-  mScrollFrame->RemoveScrollPositionListener(this);
+  mScrollContainerFrame->RemoveScrollPositionListener(this);
 }
 
 // static
@@ -167,7 +167,7 @@ void StickyScrollContainer::ComputeStickyLimits(nsIFrame* aFrame,
     return;
   }
 
-  nsIFrame* scrolledFrame = mScrollFrame->GetScrolledFrame();
+  nsIFrame* scrolledFrame = mScrollContainerFrame->GetScrolledFrame();
   nsIFrame* cbFrame = aFrame->GetContainingBlock();
   NS_ASSERTION(cbFrame == scrolledFrame ||
                    nsLayoutUtils::IsProperAncestorFrame(scrolledFrame, cbFrame),
@@ -376,7 +376,7 @@ void StickyScrollContainer::UpdatePositions(nsPoint aScrollPosition,
                                             nsIFrame* aSubtreeRoot) {
 #ifdef DEBUG
   {
-    nsIFrame* scrollFrameAsFrame = do_QueryFrame(mScrollFrame);
+    nsIFrame* scrollFrameAsFrame = do_QueryFrame(mScrollContainerFrame);
     NS_ASSERTION(!aSubtreeRoot || aSubtreeRoot == scrollFrameAsFrame,
                  "If reflowing, should be reflowing the scroll frame");
   }
diff --git a/layout/generic/StickyScrollContainer.h b/layout/generic/StickyScrollContainer.h
index 64f2aea5086d..58a78b15b18b 100644
--- a/layout/generic/StickyScrollContainer.h
+++ b/layout/generic/StickyScrollContainer.h
@@ -19,10 +19,11 @@
 
 struct nsRect;
 class nsIFrame;
-class nsIScrollableFrame;
 
 namespace mozilla {
 
+class ScrollContainerFrame;
+
 class StickyScrollContainer final : public nsIScrollPositionListener {
  public:
   /**
@@ -48,7 +49,9 @@ class StickyScrollContainer final : public nsIScrollPositionListener {
   void AddFrame(nsIFrame* aFrame) { mFrames.AppendElement(aFrame); }
   void RemoveFrame(nsIFrame* aFrame) { mFrames.RemoveElement(aFrame); }
 
-  nsIScrollableFrame* ScrollFrame() const { return mScrollFrame; }
+  ScrollContainerFrame* ScrollContainer() const {
+    return mScrollContainerFrame;
+  }
 
   // Compute the offsets for a sticky position element
   static void ComputeStickyOffsets(nsIFrame* aFrame);
@@ -94,7 +97,7 @@ class StickyScrollContainer final : public nsIScrollPositionListener {
   bool IsStuckInYDirection(nsIFrame* aFrame) const;
 
  private:
-  explicit StickyScrollContainer(nsIScrollableFrame* aScrollFrame);
+  explicit StickyScrollContainer(ScrollContainerFrame* aScrollContainerFrame);
 
   /**
    * Compute two rectangles that determine sticky positioning: |aStick|, based
@@ -105,7 +108,7 @@ class StickyScrollContainer final : public nsIScrollPositionListener {
   void ComputeStickyLimits(nsIFrame* aFrame, nsRect* aStick,
                            nsRect* aContain) const;
 
-  nsIScrollableFrame* const mScrollFrame;
+  ScrollContainerFrame* const mScrollContainerFrame;
   nsTArray<nsIFrame*> mFrames;
   nsPoint mScrollPosition;
 };
diff --git a/layout/generic/ViewportFrame.cpp b/layout/generic/ViewportFrame.cpp
index feb24ebbf9c7..65e748a89513 100644
--- a/layout/generic/ViewportFrame.cpp
+++ b/layout/generic/ViewportFrame.cpp
@@ -15,8 +15,8 @@
 #include "mozilla/PresShell.h"
 #include "mozilla/ProfilerLabels.h"
 #include "mozilla/RestyleManager.h"
+#include "mozilla/ScrollContainerFrame.h"
 #include "nsGkAtoms.h"
-#include "nsIScrollableFrame.h"
 #include "nsAbsoluteContainingBlock.h"
 #include "nsCanvasFrame.h"
 #include "nsLayoutUtils.h"
@@ -287,11 +287,11 @@ nsPoint ViewportFrame::AdjustReflowInputForScrollbars(
     ReflowInput* aReflowInput) const {
   // Get our prinicpal child frame and see if we're scrollable
   nsIFrame* kidFrame = mFrames.FirstChild();
-  nsIScrollableFrame* scrollingFrame = do_QueryFrame(kidFrame);
 
-  if (scrollingFrame) {
+  if (ScrollContainerFrame* scrollContainerFrame = do_QueryFrame(kidFrame)) {
     WritingMode wm = aReflowInput->GetWritingMode();
-    LogicalMargin scrollbars(wm, scrollingFrame->GetActualScrollbarSizes());
+    LogicalMargin scrollbars(wm,
+                             scrollContainerFrame->GetActualScrollbarSizes());
     aReflowInput->SetComputedISize(
         aReflowInput->ComputedISize() - scrollbars.IStartEnd(wm),
         ReflowInput::ResetResizeFlags::No);
diff --git a/layout/generic/nsBlockFrame.cpp b/layout/generic/nsBlockFrame.cpp
index 72e822e48d01..e94d9156d4c7 100644
--- a/layout/generic/nsBlockFrame.cpp
+++ b/layout/generic/nsBlockFrame.cpp
@@ -19,6 +19,7 @@
 #include "mozilla/DebugOnly.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/PresShell.h"
+#include "mozilla/ScrollContainerFrame.h"
 #include "mozilla/StaticPrefs_browser.h"
 #include "mozilla/StaticPrefs_layout.h"
 #include "mozilla/ToString.h"
@@ -45,7 +46,6 @@
 #include "nsFloatManager.h"
 #include "prenv.h"
 #include "nsError.h"
-#include "nsIScrollableFrame.h"
 #include <algorithm>
 #include "nsLayoutUtils.h"
 #include "nsDisplayList.h"
@@ -1126,11 +1126,10 @@ static LogicalSize CalculateContainingBlockSizeForAbsolutes(
 
   // For scroll containers, we can just use cbSize (which is the padding-box
   // size of the scrolled-content frame).
-  if (nsIScrollableFrame* scrollFrame = do_QueryFrame(lastRI->mFrame)) {
+  if (lastRI->mFrame->IsScrollContainerOrSubclass()) {
     // Assert that we're not missing any frames between the abspos containing
     // block and the scroll container.
     // the parent.
-    Unused << scrollFrame;
     MOZ_ASSERT(lastButOneRI == &aReflowInput);
     return cbSize;
   }
diff --git a/layout/generic/nsCanvasFrame.cpp b/layout/generic/nsCanvasFrame.cpp
index c8b0b8f85c21..169a7b6873ec 100644
--- a/layout/generic/nsCanvasFrame.cpp
+++ b/layout/generic/nsCanvasFrame.cpp
@@ -278,9 +278,8 @@ nsRect nsCanvasFrame::CanvasArea() const {
   // matter.
   nsRect result(InkOverflowRect());
 
-  nsIScrollableFrame* scrollableFrame = do_QueryFrame(GetParent());
-  if (scrollableFrame) {
-    nsRect portRect = scrollableFrame->GetScrollPortRect();
+  if (ScrollContainerFrame* scrollContainerFrame = do_QueryFrame(GetParent())) {
+    nsRect portRect = scrollContainerFrame->GetScrollPortRect();
     result.UnionRect(result, nsRect(nsPoint(0, 0), portRect.Size()));
   }
   return result;
@@ -587,12 +586,11 @@ void nsCanvasFrame::BuildDisplayList(nsDisplayListBuilder* aBuilder,
 void nsCanvasFrame::PaintFocus(DrawTarget* aDrawTarget, nsPoint aPt) {
   nsRect focusRect(aPt, GetSize());
 
-  nsIScrollableFrame* scrollableFrame = do_QueryFrame(GetParent());
-  if (scrollableFrame) {
-    nsRect portRect = scrollableFrame->GetScrollPortRect();
+  if (ScrollContainerFrame* scrollContainerFrame = do_QueryFrame(GetParent())) {
+    nsRect portRect = scrollContainerFrame->GetScrollPortRect();
     focusRect.width = portRect.width;
     focusRect.height = portRect.height;
-    focusRect.MoveBy(scrollableFrame->GetScrollPosition());
+    focusRect.MoveBy(scrollContainerFrame->GetScrollPosition());
   }
 
   // XXX use the root frame foreground color, but should we find BODY frame
diff --git a/layout/generic/nsFrameSelection.cpp b/layout/generic/nsFrameSelection.cpp
index 924802d600a0..b0bd92e53698 100644
--- a/layout/generic/nsFrameSelection.cpp
+++ b/layout/generic/nsFrameSelection.cpp
@@ -1662,16 +1662,16 @@ nsIFrame* nsFrameSelection::GetFrameToPageSelect() const {
     // parent under the root frame.
     for (nsIFrame* frame = contentToSelect->GetPrimaryFrame();
          frame && frame != rootFrameToSelect; frame = frame->GetParent()) {
-      nsIScrollableFrame* scrollableFrame = do_QueryFrame(frame);
-      if (!scrollableFrame) {
+      ScrollContainerFrame* scrollContainerFrame = do_QueryFrame(frame);
+      if (!scrollContainerFrame) {
         continue;
       }
-      ScrollStyles scrollStyles = scrollableFrame->GetScrollStyles();
+      ScrollStyles scrollStyles = scrollContainerFrame->GetScrollStyles();
       if (scrollStyles.mVertical == StyleOverflow::Hidden) {
         continue;
       }
       layers::ScrollDirections directions =
-          scrollableFrame->GetAvailableScrollingDirections();
+          scrollContainerFrame->GetAvailableScrollingDirections();
       if (directions.contains(layers::ScrollDirection::eVertical)) {
         // If there is sub scrollable frame, let's use its page size to select.
         return frame;
diff --git a/layout/generic/nsFrameSelection.h b/layout/generic/nsFrameSelection.h
index bbc9f9dc1d44..5c517df3f112 100644
--- a/layout/generic/nsFrameSelection.h
+++ b/layout/generic/nsFrameSelection.h
@@ -217,7 +217,6 @@ enum class TableSelectionMode : uint32_t {
 };
 
 }  // namespace mozilla
-class nsIScrollableFrame;
 
 class nsFrameSelection final {
  public:
diff --git a/layout/generic/nsGridContainerFrame.cpp b/layout/generic/nsGridContainerFrame.cpp
index faced8474489..5f064736ffab 100644
--- a/layout/generic/nsGridContainerFrame.cpp
+++ b/layout/generic/nsGridContainerFrame.cpp
@@ -7542,7 +7542,7 @@ nsGridContainerFrame::GetNearestFragmentainer(
   WritingMode wm = aState.mWM;
   const ReflowInput* cbRI = gridRI->mCBReflowInput;
   for (; cbRI; cbRI = cbRI->mCBReflowInput) {
-    nsIScrollableFrame* sf = do_QueryFrame(cbRI->mFrame);
+    ScrollContainerFrame* sf = do_QueryFrame(cbRI->mFrame);
     if (sf) {
       break;
     }
diff --git a/layout/generic/nsIFrame.cpp b/layout/generic/nsIFrame.cpp
index 35fa6c37772d..74a19dd8cafd 100644
--- a/layout/generic/nsIFrame.cpp
+++ b/layout/generic/nsIFrame.cpp
@@ -1217,8 +1217,8 @@ void nsIFrame::DidSetComputedStyle(ComputedStyle* aOldComputedStyle) {
       if (auto* container = ScrollAnchorContainer::FindFor(this)) {
         container->InvalidateAnchor();
       }
-      if (nsIScrollableFrame* scrollableFrame = do_QueryFrame(this)) {
-        scrollableFrame->Anchor()->InvalidateAnchor();
+      if (ScrollContainerFrame* scrollContainerFrame = do_QueryFrame(this)) {
+        scrollContainerFrame->Anchor()->InvalidateAnchor();
       }
     }
 
@@ -2185,8 +2185,7 @@ void nsIFrame::UpdateVisibilitySynchronously() {
   nsRect rect = GetRectRelativeToSelf();
   nsIFrame* rectFrame = this;
   while (f && visible) {
-    nsIScrollableFrame* sf = do_QueryFrame(f);
-    if (sf) {
+    if (ScrollContainerFrame* sf = do_QueryFrame(f)) {
       nsRect transformedRect =
           nsLayoutUtils::TransformFrameRectToAncestor(rectFrame, rect, f);
       if (!sf->IsRectNearlyVisible(transformedRect)) {
@@ -3785,8 +3784,8 @@ void nsIFrame::BuildDisplayListForStackingContext(
 
     StickyScrollContainer* stickyScrollContainer =
         StickyScrollContainer::GetStickyScrollContainerForFrame(this);
-    if (stickyScrollContainer &&
-        stickyScrollContainer->ScrollFrame()->IsMaybeAsynchronouslyScrolled()) {
+    if (stickyScrollContainer && stickyScrollContainer->ScrollContainer()
+                                     ->IsMaybeAsynchronouslyScrolled()) {
       shouldFlatten = false;
     }
 
@@ -10799,17 +10798,17 @@ bool nsIFrame::IsFocusableDueToScrollFrame() {
   // with the mouse, because the extra focus outlines are considered
   // unnecessarily ugly.  When clicked on, the selection position within the
   // element will be enough to make them keyboard scrollable.
-  nsIScrollableFrame* scrollFrame = do_QueryFrame(this);
-  if (!scrollFrame) {
+  ScrollContainerFrame* scrollContainerFrame = do_QueryFrame(this);
+  if (!scrollContainerFrame) {
     return false;
   }
-  if (scrollFrame->IsForTextControlWithNoScrollbars()) {
+  if (scrollContainerFrame->IsForTextControlWithNoScrollbars()) {
     return false;
   }
-  if (scrollFrame->GetScrollStyles().IsHiddenInBothDirections()) {
+  if (scrollContainerFrame->GetScrollStyles().IsHiddenInBothDirections()) {
     return false;
   }
-  if (scrollFrame->GetScrollRange().IsEqualEdges(nsRect(0, 0, 0, 0))) {
+  if (scrollContainerFrame->GetScrollRange().IsEqualEdges(nsRect(0, 0, 0, 0))) {
     return false;
   }
   return true;
@@ -11174,8 +11173,8 @@ static bool IsFrameScrolledOutOfView(const nsIFrame* aTarget,
   // subtree
   for (nsIFrame* f = const_cast<nsIFrame*>(aParent); f;
        f = nsLayoutUtils::GetCrossDocParentFrameInProcess(f)) {
-    nsIScrollableFrame* scrollableFrame = do_QueryFrame(f);
-    if (scrollableFrame) {
+    ScrollContainerFrame* scrollContainerFrame = do_QueryFrame(f);
+    if (scrollContainerFrame) {
       clipParent = f;
       break;
     }
diff --git a/layout/generic/nsIScrollPositionListener.h b/layout/generic/nsIScrollPositionListener.h
index eadae2fe0c78..12b4f49a2ebc 100644
--- a/layout/generic/nsIScrollPositionListener.h
+++ b/layout/generic/nsIScrollPositionListener.h
@@ -11,7 +11,7 @@
 
 /**
  * Provides a way to learn about scroll position changes of
- * nsIScrollableFrame's.
+ * ScrollContainerFrame's.
  */
 class nsIScrollPositionListener {
  public:
diff --git a/layout/painting/DisplayItemClipChain.h b/layout/painting/DisplayItemClipChain.h
index 64917dd9f6cb..c1e39b707de6 100644
--- a/layout/painting/DisplayItemClipChain.h
+++ b/layout/painting/DisplayItemClipChain.h
@@ -11,8 +11,6 @@
 #include "DisplayItemClip.h"
 #include "nsString.h"
 
-class nsIScrollableFrame;
-
 namespace mozilla {
 
 struct ActiveScrolledRoot;
diff --git a/layout/painting/DisplayListClipState.h b/layout/painting/DisplayListClipState.h
index 0f1df2ca5882..1c9451606fc8 100644
--- a/layout/painting/DisplayListClipState.h
+++ b/layout/painting/DisplayListClipState.h
@@ -13,7 +13,6 @@
 #include "mozilla/DebugOnly.h"
 
 class nsIFrame;
-class nsIScrollableFrame;
 
 namespace mozilla {
 
diff --git a/layout/painting/RetainedDisplayListBuilder.cpp b/layout/painting/RetainedDisplayListBuilder.cpp
index 028677dfb440..eaf9a9304a6c 100644
--- a/layout/painting/RetainedDisplayListBuilder.cpp
+++ b/layout/painting/RetainedDisplayListBuilder.cpp
@@ -973,7 +973,7 @@ static bool ProcessFrameInternal(nsIFrame* aFrame,
 
     // Check whether the current frame is a scrollable frame with display port.
     nsRect displayPort;
-    nsIScrollableFrame* sf = do_QueryFrame(currentFrame);
+    ScrollContainerFrame* sf = do_QueryFrame(currentFrame);
     nsIContent* content = sf ? currentFrame->GetContent() : nullptr;
 
     if (content && DisplayPortUtils::GetDisplayPort(content, &displayPort)) {
diff --git a/layout/painting/nsCSSRendering.cpp b/layout/painting/nsCSSRendering.cpp
index eede2ac2321f..021e1fabba50 100644
--- a/layout/painting/nsCSSRendering.cpp
+++ b/layout/painting/nsCSSRendering.cpp
@@ -2184,15 +2184,15 @@ void nsCSSRendering::GetImageLayerClip(
     // like the content. (See below.)
     // Therefore, only 'content-box' makes a difference here.
     if (layerClip == StyleGeometryBox::ContentBox) {
-      nsIScrollableFrame* scrollableFrame = do_QueryFrame(aForFrame);
+      ScrollContainerFrame* scrollContainerFrame = do_QueryFrame(aForFrame);
       // Clip at a rectangle attached to the scrolled content.
       aClipState->mHasAdditionalBGClipArea = true;
       aClipState->mAdditionalBGClipArea =
           nsRect(aClipState->mBGClipArea.TopLeft() +
-                     scrollableFrame->GetScrolledFrame()->GetPosition()
+                     scrollContainerFrame->GetScrolledFrame()->GetPosition()
                      // For the dir=rtl case:
-                     + scrollableFrame->GetScrollRange().TopLeft(),
-                 scrollableFrame->GetScrolledRect().Size());
+                     + scrollContainerFrame->GetScrollRange().TopLeft(),
+                 scrollContainerFrame->GetScrolledRect().Size());
       nsMargin padding = aForFrame->GetUsedPadding();
       // padding-bottom is ignored on scrollable frames:
       // https://bugzilla.mozilla.org/show_bug.cgi?id=748518
@@ -2771,11 +2771,12 @@ nsRect nsCSSRendering::ComputeImageLayerPositioningArea(
   nsIFrame* geometryFrame = aForFrame;
   if (MOZ_UNLIKELY(frameType == LayoutFrameType::ScrollContainer &&
                    StyleImageLayerAttachment::Local == aLayer.mAttachment)) {
-    nsIScrollableFrame* scrollableFrame = do_QueryFrame(aForFrame);
-    positionArea = nsRect(scrollableFrame->GetScrolledFrame()->GetPosition()
-                              // For the dir=rtl case:
-                              + scrollableFrame->GetScrollRange().TopLeft(),
-                          scrollableFrame->GetScrolledRect().Size());
+    ScrollContainerFrame* scrollContainerFrame = do_QueryFrame(aForFrame);
+    positionArea =
+        nsRect(scrollContainerFrame->GetScrolledFrame()->GetPosition()
+                   // For the dir=rtl case:
+                   + scrollContainerFrame->GetScrollRange().TopLeft(),
+               scrollContainerFrame->GetScrolledRect().Size());
     // The ScrolledRect’s size does not include the borders or scrollbars,
     // reverse the handling of background-origin
     // compared to the common case below.
@@ -2783,7 +2784,7 @@ nsRect nsCSSRendering::ComputeImageLayerPositioningArea(
       nsMargin border = geometryFrame->GetUsedBorder();
       border.ApplySkipSides(geometryFrame->GetSkipSides());
       positionArea.Inflate(border);
-      positionArea.Inflate(scrollableFrame->GetActualScrollbarSizes());
+      positionArea.Inflate(scrollContainerFrame->GetActualScrollbarSizes());
     } else if (layerOrigin != StyleGeometryBox::PaddingBox) {
       nsMargin padding = geometryFrame->GetUsedPadding();
       padding.ApplySkipSides(geometryFrame->GetSkipSides());
diff --git a/layout/painting/nsDisplayList.cpp b/layout/painting/nsDisplayList.cpp
index 27e942ffe545..4bed18efb41e 100644
--- a/layout/painting/nsDisplayList.cpp
+++ b/layout/painting/nsDisplayList.cpp
@@ -912,16 +912,16 @@ bool nsDisplayListBuilder::ShouldRebuildDisplayListDueToPrefChange() {
   return false;
 }
 
-void nsDisplayListBuilder::AddScrollFrameToNotify(
-    nsIScrollableFrame* aScrollFrame) {
-  mScrollFramesToNotify.insert(aScrollFrame);
+void nsDisplayListBuilder::AddScrollContainerFrameToNotify(
+    ScrollContainerFrame* aScrollContainerFrame) {
+  mScrollContainerFramesToNotify.insert(aScrollContainerFrame);
 }
 
-void nsDisplayListBuilder::NotifyAndClearScrollFrames() {
-  for (const auto& it : mScrollFramesToNotify) {
+void nsDisplayListBuilder::NotifyAndClearScrollContainerFrames() {
+  for (const auto& it : mScrollContainerFramesToNotify) {
     it->NotifyApzTransaction();
   }
-  mScrollFramesToNotify.clear();
+  mScrollContainerFramesToNotify.clear();
 }
 
 bool nsDisplayListBuilder::MarkOutOfFlowFrameForDisplay(
@@ -1621,8 +1621,8 @@ static bool IsStickyFrameActive(nsDisplayListBuilder* aBuilder,
 
   StickyScrollContainer* stickyScrollContainer =
       StickyScrollContainer::GetStickyScrollContainerForFrame(aFrame);
-  return stickyScrollContainer &&
-         stickyScrollContainer->ScrollFrame()->IsMaybeAsynchronouslyScrolled();
+  return stickyScrollContainer && stickyScrollContainer->ScrollContainer()
+                                      ->IsMaybeAsynchronouslyScrolled();
 }
 
 bool nsDisplayListBuilder::IsAnimatedGeometryRoot(nsIFrame* aFrame,
@@ -1657,7 +1657,7 @@ bool nsDisplayListBuilder::IsAnimatedGeometryRoot(nsIFrame* aFrame,
   }
 
   if (parent->IsScrollContainerOrSubclass()) {
-    nsIScrollableFrame* sf = do_QueryFrame(parent);
+    ScrollContainerFrame* sf = do_QueryFrame(parent);
     if (sf->GetScrolledFrame() == aFrame) {
       MOZ_ASSERT(!aFrame->IsTransformed());
       return sf->IsMaybeAsynchronouslyScrolled();
@@ -5582,9 +5582,9 @@ StickyScrollContainer* nsDisplayStickyPosition::GetStickyScrollContainer() {
     // will never be asynchronously scrolled. Instead we will always position
     // the sticky items correctly on the gecko side and WR will never need to
     // adjust their position itself.
-    MOZ_ASSERT(
-        stickyScrollContainer->ScrollFrame()->IsMaybeAsynchronouslyScrolled());
-    if (!stickyScrollContainer->ScrollFrame()
+    MOZ_ASSERT(stickyScrollContainer->ScrollContainer()
+                   ->IsMaybeAsynchronouslyScrolled());
+    if (!stickyScrollContainer->ScrollContainer()
              ->IsMaybeAsynchronouslyScrolled()) {
       stickyScrollContainer = nullptr;
     }
@@ -5618,14 +5618,14 @@ bool nsDisplayStickyPosition::CreateWebRenderCommands(
     nsRectAbsolute inner;
     stickyScrollContainer->GetScrollRanges(mFrame, &outer, &inner);
 
-    nsIFrame* scrollFrame = do_QueryFrame(stickyScrollContainer->ScrollFrame());
     nsPoint offset =
-        scrollFrame->GetOffsetToCrossDoc(Frame()) + ToReferenceFrame();
+        stickyScrollContainer->ScrollContainer()->GetOffsetToCrossDoc(Frame()) +
+        ToReferenceFrame();
 
     // Adjust the scrollPort coordinates to be relative to the reference frame,
     // so that it is in the same space as everything else.
     nsRect scrollPort =
-        stickyScrollContainer->ScrollFrame()->GetScrollPortRect();
+        stickyScrollContainer->ScrollContainer()->GetScrollPortRect();
     scrollPort += offset;
 
     // The following computations make more sense upon understanding the
@@ -5821,10 +5821,10 @@ bool nsDisplayStickyPosition::UpdateScrollData(
           nsLayoutUtils::GetSideBitsForFixedPositionContent(mFrame);
       aLayerData->SetFixedPositionSides(sides);
 
-      ScrollableLayerGuid::ViewID scrollId =
-          nsLayoutUtils::FindOrCreateIDFor(stickyScrollContainer->ScrollFrame()
-                                               ->GetScrolledFrame()
-                                               ->GetContent());
+      ScrollableLayerGuid::ViewID scrollId = nsLayoutUtils::FindOrCreateIDFor(
+          stickyScrollContainer->ScrollContainer()
+              ->GetScrolledFrame()
+              ->GetContent());
       aLayerData->SetStickyPositionScrollContainerId(scrollId);
     }
 
@@ -5869,7 +5869,7 @@ UniquePtr<ScrollMetadata> nsDisplayScrollInfoLayer::ComputeScrollMetadata(
   ScrollContainerFrame* scrollContainerFrame =
       mScrollFrame->GetScrollTargetFrame();
   if (scrollContainerFrame) {
-    aBuilder->AddScrollFrameToNotify(scrollContainerFrame);
+    aBuilder->AddScrollContainerFrameToNotify(scrollContainerFrame);
   }
 
   return UniquePtr<ScrollMetadata>(new ScrollMetadata(metadata));
@@ -5960,9 +5960,10 @@ void nsDisplayAsyncZoom::HitTest(nsDisplayListBuilder* aBuilder,
                                  const nsRect& aRect, HitTestState* aState,
                                  nsTArray<nsIFrame*>* aOutFrames) {
 #ifdef DEBUG
-  nsIScrollableFrame* scrollFrame = do_QueryFrame(mFrame);
-  MOZ_ASSERT(scrollFrame && ViewportUtils::IsZoomedContentRoot(
-                                scrollFrame->GetScrolledFrame()));
+  ScrollContainerFrame* scrollContainerFrame = do_QueryFrame(mFrame);
+  MOZ_ASSERT(scrollContainerFrame &&
+             ViewportUtils::IsZoomedContentRoot(
+                 scrollContainerFrame->GetScrolledFrame()));
 #endif
   nsRect rect = ViewportUtils::VisualToLayout(aRect, mFrame->PresShell());
   mList.HitTest(aBuilder, rect, aState, aOutFrames);
diff --git a/layout/painting/nsDisplayList.h b/layout/painting/nsDisplayList.h
index c1e4f4104980..22b35e293b26 100644
--- a/layout/painting/nsDisplayList.h
+++ b/layout/painting/nsDisplayList.h
@@ -65,7 +65,6 @@
 
 class gfxContext;
 class nsIContent;
-class nsIScrollableFrame;
 class nsSubDocumentFrame;
 class nsCaret;
 struct WrFiltersHolder;
@@ -1643,8 +1642,9 @@ class nsDisplayListBuilder {
     }
   };
 
-  void AddScrollFrameToNotify(nsIScrollableFrame* aScrollFrame);
-  void NotifyAndClearScrollFrames();
+  void AddScrollContainerFrameToNotify(
+      ScrollContainerFrame* aScrollContainerFrame);
+  void NotifyAndClearScrollContainerFrames();
 
   // Helper class to find what link spec (if any) to associate with a frame,
   // recording it in the builder, and generate the corresponding DisplayItem.
@@ -1829,7 +1829,7 @@ class nsDisplayListBuilder {
   std::unordered_set<const DisplayItemClipChain*, DisplayItemClipChainHasher,
                      DisplayItemClipChainEqualer>
       mClipDeduplicator;
-  std::unordered_set<nsIScrollableFrame*> mScrollFramesToNotify;
+  std::unordered_set<ScrollContainerFrame*> mScrollContainerFramesToNotify;
 
   AutoTArray<nsIFrame*, 20> mFramesWithOOFData;
   AutoTArray<nsIFrame*, 40> mFramesMarkedForDisplayIfVisible;
diff --git a/layout/style/nsComputedDOMStyle.cpp b/layout/style/nsComputedDOMStyle.cpp
index fbf4c0e0cbc2..744024a2b1d6 100644
--- a/layout/style/nsComputedDOMStyle.cpp
+++ b/layout/style/nsComputedDOMStyle.cpp
@@ -23,7 +23,6 @@
 #include "nsIFrame.h"
 #include "nsIFrameInlines.h"
 #include "mozilla/ComputedStyle.h"
-#include "nsIScrollableFrame.h"
 #include "nsContentUtils.h"
 #include "nsDocShell.h"
 #include "nsIContent.h"
@@ -2014,9 +2013,9 @@ nscoord nsComputedDOMStyle::GetUsedAbsoluteOffset(mozilla::Side aSide) {
     // scrollbars.  We have to do some extra work.
     // the first child in the default frame list is what we want
     nsIFrame* scrollingChild = container->PrincipalChildList().FirstChild();
-    nsIScrollableFrame* scrollFrame = do_QueryFrame(scrollingChild);
-    if (scrollFrame) {
-      scrollbarSizes = scrollFrame->GetActualScrollbarSizes();
+    ScrollContainerFrame* scrollContainerFrame = do_QueryFrame(scrollingChild);
+    if (scrollContainerFrame) {
+      scrollbarSizes = scrollContainerFrame->GetActualScrollbarSizes();
     }
 
     // The viewport size might have been expanded by the visual viewport or
diff --git a/layout/tables/nsTableCellFrame.cpp b/layout/tables/nsTableCellFrame.cpp
index 6a8d777c97b1..6312cc79f9d4 100644
--- a/layout/tables/nsTableCellFrame.cpp
+++ b/layout/tables/nsTableCellFrame.cpp
@@ -533,7 +533,7 @@ static bool CellHasVisibleContent(nsTableFrame* aTableFrame,
 
 nsIFrame* nsTableCellFrame::CellContentFrame() const {
   nsIFrame* inner = mFrames.FirstChild();
-  if (nsIScrollableFrame* sf = do_QueryFrame(inner)) {
+  if (ScrollContainerFrame* sf = do_QueryFrame(inner)) {
     return sf->GetScrolledFrame();
   }
   return inner;
diff --git a/layout/tables/nsTableFrame.cpp b/layout/tables/nsTableFrame.cpp
index e03af22e4cbf..f9076ef9032f 100644
--- a/layout/tables/nsTableFrame.cpp
+++ b/layout/tables/nsTableFrame.cpp
@@ -47,7 +47,6 @@
 #include "mozilla/RestyleManager.h"
 #include "mozilla/ServoStyleSet.h"
 #include "nsDisplayList.h"
-#include "nsIScrollableFrame.h"
 #include "nsCSSProps.h"
 #include "nsLayoutUtils.h"
 #include "nsStyleChangeList.h"
diff --git a/layout/xul/nsMenuPopupFrame.cpp b/layout/xul/nsMenuPopupFrame.cpp
index 17993c84665f..68ba2a1a75e9 100644
--- a/layout/xul/nsMenuPopupFrame.cpp
+++ b/layout/xul/nsMenuPopupFrame.cpp
@@ -24,7 +24,6 @@
 #include "nsFrameManager.h"
 #include "mozilla/dom/Document.h"
 #include "nsRect.h"
-#include "nsIScrollableFrame.h"
 #include "nsIPopupContainer.h"
 #include "nsIDocShell.h"
 #include "nsReadableUtils.h"
@@ -53,6 +52,7 @@
 #include "mozilla/LookAndFeel.h"
 #include "mozilla/MouseEvents.h"
 #include "mozilla/PresShell.h"
+#include "mozilla/ScrollContainerFrame.h"
 #include "mozilla/Services.h"
 #include "mozilla/dom/BrowserParent.h"
 #include "mozilla/dom/Element.h"
@@ -472,7 +472,7 @@ void nsMenuPopupFrame::TweakMinPrefISize(nscoord& aSize) {
   //
   // Automatically accommodating for the scrollbar otherwise would be bug
   // 764076, but that has its own set of problems.
-  if (nsIScrollableFrame* sf = GetScrollFrame()) {
+  if (ScrollContainerFrame* sf = GetScrollContainerFrame()) {
     aSize += sf->GetDesiredScrollbarSizes().LeftRight();
   }
 
@@ -1170,7 +1170,7 @@ nsPoint nsMenuPopupFrame::AdjustPositionForAnchorAlign(
         // popup up in a way that our box would no longer intersect with the
         // anchor.
         nscoord maxOffset = aPrefSize.height - itemHeight;
-        if (const nsIScrollableFrame* sf = GetScrollFrame()) {
+        if (const ScrollContainerFrame* sf = GetScrollContainerFrame()) {
           // HACK: We ideally would want to use the offset from the bottom
           // bottom of our scroll-frame to the bottom of our frame (so as to
           // ensure that the bottom of the scrollport is inside the anchor
@@ -1183,8 +1183,7 @@ nsPoint nsMenuPopupFrame::AdjustPositionForAnchorAlign(
           // from the top. This holds for all the popups where this matters
           // (menulists on macOS, effectively), and seems better than somehow
           // moving the popup after the fact as we used to do.
-          const nsIFrame* f = do_QueryFrame(sf);
-          maxOffset -= f->GetOffsetTo(this).y;
+          maxOffset -= sf->GetOffsetTo(this).y;
         }
         mPositionedOffset =
             originalAnchorRect.height + std::min(itemOffset, maxOffset);
@@ -1905,12 +1904,12 @@ ConsumeOutsideClicksResult nsMenuPopupFrame::ConsumeOutsideClicks() {
   return ConsumeOutsideClicks_True;
 }
 
-static nsIScrollableFrame* DoGetScrollFrame(const nsIFrame* aFrame) {
-  if (const nsIScrollableFrame* sf = do_QueryFrame(aFrame)) {
-    return const_cast<nsIScrollableFrame*>(sf);
+static ScrollContainerFrame* DoGetScrollContainerFrame(const nsIFrame* aFrame) {
+  if (const ScrollContainerFrame* sf = do_QueryFrame(aFrame)) {
+    return const_cast<ScrollContainerFrame*>(sf);
   }
   for (nsIFrame* childFrame : aFrame->PrincipalChildList()) {
-    if (auto* sf = DoGetScrollFrame(childFrame)) {
+    if (auto* sf = DoGetScrollContainerFrame(childFrame)) {
       return sf;
     }
   }
@@ -1919,8 +1918,8 @@ static nsIScrollableFrame* DoGetScrollFrame(const nsIFrame* aFrame) {
 
 // XXXroc this is megalame. Fossicking around for a frame of the right
 // type is a recipe for disaster in the long term.
-nsIScrollableFrame* nsMenuPopupFrame::GetScrollFrame() const {
-  return DoGetScrollFrame(this);
+ScrollContainerFrame* nsMenuPopupFrame::GetScrollContainerFrame() const {
+  return DoGetScrollContainerFrame(this);
 }
 
 void nsMenuPopupFrame::ChangeByPage(bool aIsUp) {
@@ -1929,7 +1928,7 @@ void nsMenuPopupFrame::ChangeByPage(bool aIsUp) {
     return;
   }
 
-  nsIScrollableFrame* scrollframe = GetScrollFrame();
+  ScrollContainerFrame* scrollContainerFrame = GetScrollContainerFrame();
 
   RefPtr popup = &PopupElement();
   XULButtonElement* currentMenu = popup->GetActiveMenuChild();
@@ -1947,7 +1946,8 @@ void nsMenuPopupFrame::ChangeByPage(bool aIsUp) {
 
   if (currentMenu && currentMenu->GetPrimaryFrame()) {
     const nscoord scrollHeight =
-        scrollframe ? scrollframe->GetScrollPortRect().height : mRect.height;
+        scrollContainerFrame ? scrollContainerFrame->GetScrollPortRect().height
+                             : mRect.height;
     const nsRect currentRect = currentMenu->GetPrimaryFrame()->GetRect();
     const XULButtonElement* startMenu = currentMenu;
 
diff --git a/layout/xul/nsMenuPopupFrame.h b/layout/xul/nsMenuPopupFrame.h
index aeabdfa0bfb8..eed6b54d3a1e 100644
--- a/layout/xul/nsMenuPopupFrame.h
+++ b/layout/xul/nsMenuPopupFrame.h
@@ -24,7 +24,6 @@
 
 #include "Units.h"
 
-class nsIScrollableFrame;
 class nsIWidget;
 
 namespace mozilla {
@@ -339,7 +338,7 @@ class nsMenuPopupFrame final : public nsBlockFrame {
   void MoveToAnchor(nsIContent* aAnchorContent, const nsAString& aPosition,
                     int32_t aXPos, int32_t aYPos, bool aAttributesOverride);
 
-  nsIScrollableFrame* GetScrollFrame() const;
+  mozilla::ScrollContainerFrame* GetScrollContainerFrame() const;
 
   void SetOverrideConstraintRect(const mozilla::CSSIntRect& aRect) {
     mOverrideConstraintRect = mozilla::CSSIntRect::ToAppUnits(aRect);
diff --git a/layout/xul/nsScrollbarFrame.cpp b/layout/xul/nsScrollbarFrame.cpp
index af229af718e2..d726fb9f56a5 100644
--- a/layout/xul/nsScrollbarFrame.cpp
+++ b/layout/xul/nsScrollbarFrame.cpp
@@ -166,13 +166,13 @@ nsresult nsScrollbarFrame::AttributeChanged(int32_t aNameSpaceID,
     return rv;
   }
 
-  nsIScrollableFrame* scrollable = do_QueryFrame(GetParent());
-  if (!scrollable) {
+  ScrollContainerFrame* scrollContainerFrame = do_QueryFrame(GetParent());
+  if (!scrollContainerFrame) {
     return rv;
   }
 
   nsCOMPtr<nsIContent> content(mContent);
-  scrollable->CurPosAttributeChanged(content);
+  scrollContainerFrame->CurPosAttributeChanged(content);
   return rv;
 }
 
@@ -214,11 +214,11 @@ nsIScrollbarMediator* nsScrollbarFrame::GetScrollbarMediator() {
     return nullptr;
   }
   nsIFrame* f = mScrollbarMediator->GetPrimaryFrame();
-  nsIScrollableFrame* scrollFrame = do_QueryFrame(f);
+  ScrollContainerFrame* scrollContainerFrame = do_QueryFrame(f);
   nsIScrollbarMediator* sbm;
 
-  if (scrollFrame) {
-    nsIFrame* scrolledFrame = scrollFrame->GetScrolledFrame();
+  if (scrollContainerFrame) {
+    nsIFrame* scrolledFrame = scrollContainerFrame->GetScrolledFrame();
     sbm = do_QueryFrame(scrolledFrame);
     if (sbm) {
       return sbm;
diff --git a/layout/xul/nsSliderFrame.cpp b/layout/xul/nsSliderFrame.cpp
index 6d26f7603530..07c9ab7ce2ca 100644
--- a/layout/xul/nsSliderFrame.cpp
+++ b/layout/xul/nsSliderFrame.cpp
@@ -22,7 +22,6 @@
 #include "nsHTMLParts.h"
 #include "nsCSSRendering.h"
 #include "nsScrollbarButtonFrame.h"
-#include "nsIScrollableFrame.h"
 #include "nsIScrollbarMediator.h"
 #include "nsISupportsImpl.h"
 #include "nsScrollbarFrame.h"
@@ -38,6 +37,7 @@
 #include "mozilla/MouseEvents.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/PresShell.h"
+#include "mozilla/ScrollContainerFrame.h"
 #include "mozilla/StaticPrefs_general.h"
 #include "mozilla/StaticPrefs_layout.h"
 #include "mozilla/SVGIntegrationUtils.h"
@@ -388,9 +388,9 @@ void nsSliderFrame::BuildDisplayList(nsDisplayListBuilder* aBuilder,
   // XXX seems like this should be done in nsScrollbarFrame instead perhaps?
   if (!aBuilder->IsForEventDelivery()) {
     nsScrollbarFrame* scrollbar = Scrollbar();
-    if (nsIScrollableFrame* scrollFrame =
+    if (ScrollContainerFrame* scrollContainerFrame =
             do_QueryFrame(scrollbar->GetParent())) {
-      if (scrollFrame->IsRootScrollFrameOfDocument()) {
+      if (scrollContainerFrame->IsRootScrollFrameOfDocument()) {
         nsGlobalWindowInner* window = nsGlobalWindowInner::Cast(
             PresContext()->Document()->GetInnerWindow());
         if (window &&
@@ -408,10 +408,10 @@ static bool UsesCustomScrollbarMediator(nsIFrame* scrollbarBox) {
   if (nsScrollbarFrame* scrollbarFrame = do_QueryFrame(scrollbarBox)) {
     if (nsIScrollbarMediator* mediator =
             scrollbarFrame->GetScrollbarMediator()) {
-      nsIScrollableFrame* scrollFrame = do_QueryFrame(mediator);
-      // The scrollbar mediator is not the scroll frame.
-      // That means this scroll frame has a custom scrollbar mediator.
-      if (!scrollFrame) {
+      ScrollContainerFrame* scrollContainerFrame = do_QueryFrame(mediator);
+      // The scrollbar mediator is not the scroll container frame.
+      // That means this scroll container frame has a custom scrollbar mediator.
+      if (!scrollContainerFrame) {
         return true;
       }
     }
@@ -456,9 +456,9 @@ void nsSliderFrame::BuildDisplayListForThumb(nsDisplayListBuilder* aBuilder,
     bool isAsyncDraggable = !UsesCustomScrollbarMediator(scrollbarBox);
 
     nsPoint scrollPortOrigin;
-    if (nsIScrollableFrame* scrollFrame =
+    if (ScrollContainerFrame* scrollContainerFrame =
             do_QueryFrame(scrollbarBox->GetParent())) {
-      scrollPortOrigin = scrollFrame->GetScrollPortRect().TopLeft();
+      scrollPortOrigin = scrollContainerFrame->GetScrollPortRect().TopLeft();
     } else {
       isAsyncDraggable = false;
     }
@@ -1057,7 +1057,7 @@ static bool ScrollFrameWillBuildScrollInfoLayer(nsIFrame* aScrollFrame) {
   return false;
 }
 
-nsIScrollableFrame* nsSliderFrame::GetScrollFrame() {
+ScrollContainerFrame* nsSliderFrame::GetScrollContainerFrame() {
   return do_QueryFrame(Scrollbar()->GetParent());
 }
 
@@ -1466,11 +1466,11 @@ void nsSliderFrame::PageScroll(bool aClickAndHold) {
   }
   nsScrollbarFrame* sb = Scrollbar();
 
-  nsIScrollableFrame* sf = GetScrollFrame();
+  ScrollContainerFrame* sf = GetScrollContainerFrame();
   const ScrollSnapFlags scrollSnapFlags =
       ScrollSnapFlags::IntendedDirection | ScrollSnapFlags::IntendedEndPosition;
 
-  // If our nsIScrollbarMediator implementation is an nsIScrollableFrame,
+  // If our nsIScrollbarMediator implementation is a ScrollContainerFrame,
   // use ScrollTo() to ensure we do not scroll past the intended
   // destination. Otherwise, the combination of smooth scrolling and
   // ScrollBy() semantics (which adds the delta to the current destination
diff --git a/layout/xul/nsSliderFrame.h b/layout/xul/nsSliderFrame.h
index d47784faa31e..8eba43becfa3 100644
--- a/layout/xul/nsSliderFrame.h
+++ b/layout/xul/nsSliderFrame.h
@@ -22,6 +22,7 @@ class nsSliderFrame;
 namespace mozilla {
 class nsDisplaySliderMarks;
 class PresShell;
+class ScrollContainerFrame;
 }  // namespace mozilla
 
 nsIFrame* NS_NewSliderFrame(mozilla::PresShell* aPresShell,
@@ -152,8 +153,9 @@ class nsSliderFrame final : public nsContainerFrame {
 
   bool OnlySystemGroupDispatch(mozilla::EventMessage aMessage) const override;
 
-  // Returns the associated scrollframe that contains this slider if any.
-  nsIScrollableFrame* GetScrollFrame();
+  // Returns the associated scroll container frame that contains this slider if
+  // any.
+  mozilla::ScrollContainerFrame* GetScrollContainerFrame();
 
  private:
   bool GetScrollToClick();
diff --git a/layout/xul/tree/nsTreeBodyFrame.cpp b/layout/xul/tree/nsTreeBodyFrame.cpp
index a7eba30f8be3..c924c812c6cc 100644
--- a/layout/xul/tree/nsTreeBodyFrame.cpp
+++ b/layout/xul/tree/nsTreeBodyFrame.cpp
@@ -17,6 +17,7 @@
 #include "mozilla/MouseEvents.h"
 #include "mozilla/PresShell.h"
 #include "mozilla/ResultExtensions.h"
+#include "mozilla/ScrollContainerFrame.h"
 #include "mozilla/Try.h"
 #include "mozilla/intl/Segmenter.h"
 
@@ -57,7 +58,6 @@
 #include "mozilla/dom/NodeInfo.h"
 #include "nsContentUtils.h"
 #include "nsLayoutUtils.h"
-#include "nsIScrollableFrame.h"
 #include "nsDisplayList.h"
 #include "mozilla/dom/CustomEvent.h"
 #include "mozilla/dom/Event.h"
@@ -710,7 +710,7 @@ nsresult nsTreeBodyFrame::InvalidateRange(int32_t aStart, int32_t aEnd) {
 static void FindScrollParts(nsIFrame* aCurrFrame,
                             nsTreeBodyFrame::ScrollParts* aResult) {
   if (!aResult->mColumnsScrollFrame) {
-    nsIScrollableFrame* f = do_QueryFrame(aCurrFrame);
+    ScrollContainerFrame* f = do_QueryFrame(aCurrFrame);
     if (f) {
       aResult->mColumnsFrame = aCurrFrame;
       aResult->mColumnsScrollFrame = f;
diff --git a/layout/xul/tree/nsTreeBodyFrame.h b/layout/xul/tree/nsTreeBodyFrame.h
index d7a9498cedb8..7754aa22229a 100644
--- a/layout/xul/tree/nsTreeBodyFrame.h
+++ b/layout/xul/tree/nsTreeBodyFrame.h
@@ -32,6 +32,7 @@ class nsTreeImageListener;
 
 namespace mozilla {
 class PresShell;
+class ScrollContainerFrame;
 namespace layout {
 class ScrollbarActivity;
 }  // namespace layout
@@ -179,7 +180,7 @@ class nsTreeBodyFrame final : public mozilla::SimpleXULLeafFrame,
     nsScrollbarFrame* mHScrollbar;
     RefPtr<mozilla::dom::Element> mHScrollbarContent;
     nsIFrame* mColumnsFrame;
-    nsIScrollableFrame* mColumnsScrollFrame;
+    mozilla::ScrollContainerFrame* mColumnsScrollFrame;
   };
 
   ImgDrawResult PaintTreeBody(gfxContext& aRenderingContext,
diff --git a/toolkit/components/sessionstore/SessionStoreUtils.cpp b/toolkit/components/sessionstore/SessionStoreUtils.cpp
index 3c0eaa00e4d4..6a103bd13bb4 100644
--- a/toolkit/components/sessionstore/SessionStoreUtils.cpp
+++ b/toolkit/components/sessionstore/SessionStoreUtils.cpp
@@ -53,7 +53,6 @@
 #include "nsIContentInlines.h"
 #include "nsIDocShell.h"
 #include "nsIFormControl.h"
-#include "nsIScrollableFrame.h"
 #include "nsISHistory.h"
 #include "nsIXULRuntime.h"
 #include "nsPresContext.h"
diff --git a/widget/Theme.cpp b/widget/Theme.cpp
index 1fef1e2d6b55..41f861492886 100644
--- a/widget/Theme.cpp
+++ b/widget/Theme.cpp
@@ -18,12 +18,12 @@
 #include "mozilla/gfx/Types.h"
 #include "mozilla/gfx/Filters.h"
 #include "mozilla/RelativeLuminanceUtils.h"
+#include "mozilla/ScrollContainerFrame.h"
 #include "mozilla/StaticPrefs_widget.h"
 #include "mozilla/webrender/WebRenderAPI.h"
 #include "nsCSSColorUtils.h"
 #include "nsCSSRendering.h"
 #include "nsScrollbarFrame.h"
-#include "nsIScrollableFrame.h"
 #include "nsIScrollbarMediator.h"
 #include "nsDeviceContext.h"
 #include "nsLayoutUtils.h"
@@ -1139,7 +1139,7 @@ static ScrollbarDrawing::ScrollbarKind ComputeScrollbarKind(
 
 static ScrollbarDrawing::ScrollbarKind ComputeScrollbarKindForScrollCorner(
     nsIFrame* aFrame) {
-  nsIScrollableFrame* sf = do_QueryFrame(aFrame->GetParent());
+  ScrollContainerFrame* sf = do_QueryFrame(aFrame->GetParent());
   if (!sf) {
     return ScrollbarDrawing::ScrollbarKind::VerticalRight;
   }
diff --git a/widget/cocoa/nsNativeThemeCocoa.mm b/widget/cocoa/nsNativeThemeCocoa.mm
index ad16fac04ab8..4bb570ba19c8 100644
--- a/widget/cocoa/nsNativeThemeCocoa.mm
+++ b/widget/cocoa/nsNativeThemeCocoa.mm
@@ -29,7 +29,6 @@
 #include "nsCocoaFeatures.h"
 #include "nsCocoaWindow.h"
 #include "nsNativeThemeColors.h"
-#include "nsIScrollableFrame.h"
 #include "mozilla/ClearOnShutdown.h"
 #include "mozilla/Range.h"
 #include "mozilla/dom/Element.h"