diff --git a/xpfe/appshell/AppWindow.cpp b/xpfe/appshell/AppWindow.cpp
index 935ae094b4d7..e03e6540160d 100644
--- a/xpfe/appshell/AppWindow.cpp
+++ b/xpfe/appshell/AppWindow.cpp
@@ -476,16 +476,6 @@ AppWindow::GetLiveResizeListeners() {
   return listeners;
 }
 
-NS_IMETHODIMP AppWindow::AddChildWindow(nsIAppWindow* aChild) {
-  // we're not really keeping track of this right now
-  return NS_OK;
-}
-
-NS_IMETHODIMP AppWindow::RemoveChildWindow(nsIAppWindow* aChild) {
-  // we're not really keeping track of this right now
-  return NS_OK;
-}
-
 NS_IMETHODIMP AppWindow::ShowModal() {
   AUTO_PROFILER_LABEL("AppWindow::ShowModal", OTHER);
 
@@ -577,11 +567,9 @@ NS_IMETHODIMP AppWindow::Destroy() {
   nsCOMPtr<nsIAppShellService> appShell(
       do_GetService(NS_APPSHELLSERVICE_CONTRACTID));
   NS_ASSERTION(appShell, "Couldn't get appShell... xpcom shutdown?");
-  if (appShell)
+  if (appShell) {
     appShell->UnregisterTopLevelWindow(static_cast<nsIAppWindow*>(this));
-
-  nsCOMPtr<nsIAppWindow> parentWindow(do_QueryReferent(mParentWindow));
-  if (parentWindow) parentWindow->RemoveChildWindow(this);
+  }
 
   // Remove modality (if any) and hide while destroying. More than
   // a convenience, the hide prevents user interaction with the partially
diff --git a/xpfe/appshell/nsAppShellService.cpp b/xpfe/appshell/nsAppShellService.cpp
index 2255df67e1b6..d895718f35f8 100644
--- a/xpfe/appshell/nsAppShellService.cpp
+++ b/xpfe/appshell/nsAppShellService.cpp
@@ -736,7 +736,6 @@ nsresult nsAppShellService::JustCreateTopWindow(
   }
 
   window.forget(aResult);
-  if (parent) parent->AddChildWindow(*aResult);
 
   if (center) rv = (*aResult)->Center(parent, parent ? false : true, false);
 
diff --git a/xpfe/appshell/nsIAppWindow.idl b/xpfe/appshell/nsIAppWindow.idl
index c72f2da4e288..3c3229071ad2 100644
--- a/xpfe/appshell/nsIAppWindow.idl
+++ b/xpfe/appshell/nsIAppWindow.idl
@@ -68,12 +68,6 @@ interface nsIAppWindow : nsISupports
 
   [noscript,notxpcom] LiveResizeListenerArray getLiveResizeListeners();
 
-  /**
-   * Tell this window that it has picked up a child XUL window
-   * @param aChild the child window being added
-   */
-  void addChildWindow(in nsIAppWindow aChild);
-
   /**
    * Returns the difference between the inner window size (client size) and the
    * outer window size, in CSS pixels.
@@ -81,12 +75,6 @@ interface nsIAppWindow : nsISupports
   [infallible] readonly attribute unsigned long outerToInnerHeightDifferenceInCSSPixels;
   [infallible] readonly attribute unsigned long outerToInnerWidthDifferenceInCSSPixels;
 
-  /**
-   * Tell this window that it has lost a child XUL window
-   * @param aChild the child window being removed
-   */
-  void removeChildWindow(in nsIAppWindow aChild);
-
   /**
    * Move the window to a centered position.
    * @param aRelative If not null, the window relative to which the window is