diff --git a/dom/base/FragmentOrElement.cpp b/dom/base/FragmentOrElement.cpp
index 01e1718532b4..764d077b1b9f 100644
--- a/dom/base/FragmentOrElement.cpp
+++ b/dom/base/FragmentOrElement.cpp
@@ -1024,8 +1024,7 @@ nsIContent::GetEventTargetParent(EventChainPreVisitor& aVisitor)
   }
 
   if (!aVisitor.mEvent->mFlags.mComposedInNativeAnonymousContent &&
-      IsRootOfNativeAnonymousSubtree() && OwnerDoc() &&
-      OwnerDoc()->GetWindow()) {
+      IsRootOfNativeAnonymousSubtree() && OwnerDoc()->GetWindow()) {
     aVisitor.SetParentTarget(OwnerDoc()->GetWindow()->GetParentTarget(), true);
   } else if (parent) {
     aVisitor.SetParentTarget(parent, false);
diff --git a/dom/canvas/CanvasRenderingContext2D.cpp b/dom/canvas/CanvasRenderingContext2D.cpp
index 82b84370b64b..b8c9341d0314 100644
--- a/dom/canvas/CanvasRenderingContext2D.cpp
+++ b/dom/canvas/CanvasRenderingContext2D.cpp
@@ -1861,7 +1861,7 @@ CanvasRenderingContext2D::RegisterAllocation()
 static already_AddRefed<LayerManager>
 LayerManagerFromCanvasElement(nsINode* aCanvasElement)
 {
-  if (!aCanvasElement || !aCanvasElement->OwnerDoc()) {
+  if (!aCanvasElement) {
     return nullptr;
   }
 
@@ -1926,7 +1926,7 @@ CanvasRenderingContext2D::TrySharedTarget(RefPtr<gfx::DrawTarget>& aOutDT,
   aOutDT = nullptr;
   aOutProvider = nullptr;
 
-  if (!mCanvasElement || !mCanvasElement->OwnerDoc()) {
+  if (!mCanvasElement) {
     return false;
   }
 
@@ -4967,8 +4967,9 @@ CanvasRenderingContext2D::IsPointInPath(JSContext* aCx, double aX, double aY, co
   // Check for site-specific permission and return false if no permission.
   if (mCanvasElement) {
     nsCOMPtr<nsIDocument> ownerDoc = mCanvasElement->OwnerDoc();
-    if (!ownerDoc || !CanvasUtils::IsImageExtractionAllowed(ownerDoc, aCx))
+    if (!CanvasUtils::IsImageExtractionAllowed(ownerDoc, aCx)) {
       return false;
+    }
   }
 
   EnsureUserSpacePath(aWinding);
@@ -5009,8 +5010,9 @@ CanvasRenderingContext2D::IsPointInStroke(JSContext* aCx, double aX, double aY)
   // Check for site-specific permission and return false if no permission.
   if (mCanvasElement) {
     nsCOMPtr<nsIDocument> ownerDoc = mCanvasElement->OwnerDoc();
-    if (!ownerDoc || !CanvasUtils::IsImageExtractionAllowed(ownerDoc, aCx))
+    if (!CanvasUtils::IsImageExtractionAllowed(ownerDoc, aCx)) {
       return false;
+    }
   }
 
   EnsureUserSpacePath();
@@ -5878,8 +5880,7 @@ CanvasRenderingContext2D::GetImageDataArray(JSContext* aCx,
   bool usePlaceholder = false;
   if (mCanvasElement) {
     nsCOMPtr<nsIDocument> ownerDoc = mCanvasElement->OwnerDoc();
-    usePlaceholder = !ownerDoc ||
-      !CanvasUtils::IsImageExtractionAllowed(ownerDoc, aCx);
+    usePlaceholder = !CanvasUtils::IsImageExtractionAllowed(ownerDoc, aCx);
   }
 
   do {
diff --git a/dom/ipc/TabParent.cpp b/dom/ipc/TabParent.cpp
index f93af9581b65..238837f5fef1 100644
--- a/dom/ipc/TabParent.cpp
+++ b/dom/ipc/TabParent.cpp
@@ -316,7 +316,7 @@ TabParent::SetOwnerElement(Element* aElement)
 void
 TabParent::AddWindowListeners()
 {
-  if (mFrameElement && mFrameElement->OwnerDoc()) {
+  if (mFrameElement) {
     if (nsCOMPtr<nsPIDOMWindowOuter> window = mFrameElement->OwnerDoc()->GetWindow()) {
       nsCOMPtr<EventTarget> eventTarget = window->GetTopWindowRoot();
       if (eventTarget) {
diff --git a/dom/plugins/base/nsPluginInstanceOwner.cpp b/dom/plugins/base/nsPluginInstanceOwner.cpp
index d791a3314455..c37887d7353e 100644
--- a/dom/plugins/base/nsPluginInstanceOwner.cpp
+++ b/dom/plugins/base/nsPluginInstanceOwner.cpp
@@ -497,7 +497,7 @@ NS_IMETHODIMP nsPluginInstanceOwner::GetDocument(nsIDocument* *aDocument)
 
   // XXX sXBL/XBL2 issue: current doc or owner doc?
   // But keep in mind bug 322414 comment 33
-  NS_IF_ADDREF(*aDocument = content->OwnerDoc());
+  NS_ADDREF(*aDocument = content->OwnerDoc());
   return NS_OK;
 }
 
@@ -3292,7 +3292,7 @@ void nsPluginInstanceOwner::SetFrame(nsPluginFrame *aFrame)
     }
 
     // Register for widget-focus events on the window root.
-    if (content && content->OwnerDoc() && content->OwnerDoc()->GetWindow()) {
+    if (content && content->OwnerDoc()->GetWindow()) {
       nsCOMPtr<EventTarget> windowRoot = content->OwnerDoc()->GetWindow()->GetTopWindowRoot();
       if (windowRoot) {
         windowRoot->AddEventListener(NS_LITERAL_STRING("activate"),
diff --git a/dom/svg/SVGViewportElement.h b/dom/svg/SVGViewportElement.h
index 4134c7e3c741..a0cb8ec8ca61 100644
--- a/dom/svg/SVGViewportElement.h
+++ b/dom/svg/SVGViewportElement.h
@@ -147,7 +147,7 @@ protected:
 
   bool IsRoot() const {
     NS_ASSERTION((IsInUncomposedDoc() && !GetParent()) ==
-                 (OwnerDoc() && (OwnerDoc()->GetRootElement() == this)),
+                 (OwnerDoc()->GetRootElement() == this),
                  "Can't determine if we're root");
     return IsInUncomposedDoc() && !GetParent();
   }