--- a/widget/cocoa/nsChildView.h
+++ b/widget/cocoa/nsChildView.h
@@ -555,17 +555,16 @@ protected:
   AllocateChildPopupWidget() override
   {
     static NS_DEFINE_IID(kCPopUpCID, NS_POPUP_CID);
     nsCOMPtr<nsIWidget> widget = do_CreateInstance(kCPopUpCID);
     return widget.forget();
   }
 
   void ConfigureAPZCTreeManager() override;
-  void ConfigureAPZControllerThread() override;
 
   void DoRemoteComposition(const nsIntRect& aRenderRect);
 
   // Overlay drawing functions for OpenGL drawing
   void DrawWindowOverlay(mozilla::layers::GLManager* aManager, nsIntRect aRect);
   void MaybeDrawResizeIndicator(mozilla::layers::GLManager* aManager, const nsIntRect& aRect);
   void MaybeDrawRoundedCorners(mozilla::layers::GLManager* aManager, const nsIntRect& aRect);
   void MaybeDrawTitlebar(mozilla::layers::GLManager* aManager, const nsIntRect& aRect);

--- a/widget/cocoa/nsChildView.mm
+++ b/widget/cocoa/nsChildView.mm
@@ -55,17 +55,16 @@
 #include "mozilla/layers/LayerManagerComposite.h"
 #include "GLTextureImage.h"
 #include "GLContextProvider.h"
 #include "GLContextCGL.h"
 #include "GLUploadHelpers.h"
 #include "ScopedGLHelpers.h"
 #include "HeapCopyOfStackArray.h"
 #include "mozilla/layers/APZCTreeManager.h"
-#include "mozilla/layers/APZThreadUtils.h"
 #include "mozilla/layers/GLManager.h"
 #include "mozilla/layers/CompositorOGL.h"
 #include "mozilla/layers/CompositorParent.h"
 #include "mozilla/layers/BasicCompositor.h"
 #include "gfxUtils.h"
 #include "gfxPrefs.h"
 #include "mozilla/gfx/2D.h"
 #include "mozilla/gfx/BorrowedContext.h"
@@ -1886,24 +1885,16 @@ nsChildView::ConfigureAPZCTreeManager()
   nsBaseWidget::ConfigureAPZCTreeManager();
 
   if (gNumberOfWidgetsNeedingEventThread == 0) {
     [EventThreadRunner start];
   }
   gNumberOfWidgetsNeedingEventThread++;
 }
 
-void
-nsChildView::ConfigureAPZControllerThread()
-{
-  // On OS X the EventThreadRunner is the controller thread, but it doesn't
-  // have a MessageLoop.
-  APZThreadUtils::SetControllerThread(nullptr);
-}
-
 nsIntRect
 nsChildView::RectContainingTitlebarControls()
 {
   // Start with a thin strip at the top of the window for the highlight line.
   NSRect rect = NSMakeRect(0, 0, [mView bounds].size.width,
                            [(ChildView*)mView cornerRadius]);
 
   // Add the rects of the titlebar controls.