deleted file mode 100644
--- a/gfx/layers/ipc/CompositorCocoaWidgetHelper.cpp
+++ /dev/null
@@ -1,24 +0,0 @@
-/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* vim: set sw=2 ts=2 et tw=80 : */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#include "CompositorParent.h"
-#include "CompositorCocoaWidgetHelper.h"
-#include "nsDebug.h"
-
-namespace mozilla {
-namespace layers {
-namespace compositor {
-
-LayerManagerComposite*
-GetLayerManager(CompositorParent* aParent)
-{
-  return aParent->GetLayerManager();
-}
-
-
-}
-}
-}

deleted file mode 100644
--- a/gfx/layers/ipc/CompositorCocoaWidgetHelper.h
+++ /dev/null
@@ -1,29 +0,0 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
-/* vim: set sw=4 ts=8 et tw=80 : */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#ifndef mozilla_layers_CompositorCocoaWidgetHelper_h
-#define mozilla_layers_CompositorCocoaWidgetHelper_h
-
-// Note we can't include IPDL-generated headers here, since this file is being
-// used as a workaround for Bug 719036.
-
-namespace mozilla {
-namespace layers {
-
-class CompositorParent;
-class LayerManagerComposite;
-
-namespace compositor {
-
-// Needed when we cannot directly include CompositorParent.h since it includes
-// an IPDL-generated header (e.g. in widget/cocoa/nsChildView.mm; see Bug 719036).
-LayerManagerComposite* GetLayerManager(CompositorParent* aParent);
-
-}
-}
-}
-#endif // mozilla_layers_CompositorCocoaWidgetHelper_h
-

--- a/gfx/layers/ipc/CompositorParent.cpp
+++ b/gfx/layers/ipc/CompositorParent.cpp
@@ -57,16 +57,17 @@ using namespace mozilla::ipc;
 using namespace mozilla::gfx;
 using namespace std;
 
 namespace mozilla {
 namespace layers {
 
 CompositorParent::LayerTreeState::LayerTreeState()
   : mParent(nullptr)
+  , mLayerManager(nullptr)
 {
 }
 
 typedef map<uint64_t, CompositorParent::LayerTreeState> LayerTreeMap;
 static LayerTreeMap sIndirectLayerTrees;
 
 // FIXME/bug 774386: we're assuming that there's only one
 // CompositorParent, but that's not always true.  This assumption only
@@ -258,16 +259,17 @@ CompositorParent::RecvWillStop()
   // Ensure that the layer manager is destroyed before CompositorChild.
   if (mLayerManager) {
     for (LayerTreeMap::iterator it = sIndirectLayerTrees.begin();
          it != sIndirectLayerTrees.end(); it++)
     {
       LayerTreeState* lts = &it->second;
       if (lts->mParent == this) {
         mLayerManager->ClearCachedResources(lts->mRoot);
+        lts->mLayerManager = nullptr;
       }
     }
     mLayerManager->Destroy();
     mLayerManager = nullptr;
     mCompositionManager = nullptr;
   }
 
   return true;
@@ -366,16 +368,17 @@ void
 CompositorParent::ActorDestroy(ActorDestroyReason why)
 {
   mPaused = true;
   RemoveCompositor(mCompositorID);
 
   if (mLayerManager) {
     mLayerManager->Destroy();
     mLayerManager = nullptr;
+    sIndirectLayerTrees[mRootLayerTreeID].mLayerManager = nullptr;
     mCompositionManager = nullptr;
   }
 }
 
 
 void
 CompositorParent::ScheduleRenderOnCompositorThread()
 {
@@ -498,17 +501,17 @@ void
 CompositorParent::NotifyShadowTreeTransaction(uint64_t aId, bool aIsFirstPaint)
 {
   if (mApzcTreeManager &&
       mLayerManager &&
       mLayerManager->GetRoot()) {
     AutoResolveRefLayers resolve(mCompositionManager);
     mApzcTreeManager->UpdatePanZoomControllerTree(this, mLayerManager->GetRoot(), aIsFirstPaint, aId);
 
-    mLayerManager->AsLayerManagerComposite()->NotifyShadowTreeTransaction();
+    mLayerManager->NotifyShadowTreeTransaction();
   }
   ScheduleComposition();
 }
 
 // Used when layout.frame_rate is -1. Needs to be kept in sync with
 // DEFAULT_FRAME_RATE in nsRefreshDriver.cpp.
 static const int32_t kDefaultFrameRate = 60;
 
@@ -729,16 +732,17 @@ CompositorParent::InitializeLayerManager
     if (!layerManager) {
       continue;
     }
 
     layerManager->SetCompositorID(mCompositorID);
 
     if (layerManager->Initialize()) {
       mLayerManager = layerManager;
+      sIndirectLayerTrees[mRootLayerTreeID].mLayerManager = layerManager;
       return;
     }
   }
 }
 
 PLayerTransactionParent*
 CompositorParent::AllocPLayerTransactionParent(const nsTArray<LayersBackend>& aBackendHints,
                                                const uint64_t& aId,
@@ -846,16 +850,17 @@ CompositorParent::RecvNotifyChildCreated
   NotifyChildCreated(child);
   return true;
 }
 
 void
 CompositorParent::NotifyChildCreated(uint64_t aChild)
 {
   sIndirectLayerTrees[aChild].mParent = this;
+  sIndirectLayerTrees[aChild].mLayerManager = mLayerManager;
 }
 
 /*static*/ uint64_t
 CompositorParent::AllocateLayerTreeId()
 {
   MOZ_ASSERT(CompositorLoop());
   MOZ_ASSERT(NS_IsMainThread());
   static uint64_t ids = 0;
@@ -1066,18 +1071,18 @@ CrossProcessCompositorParent::ActorDestr
 PLayerTransactionParent*
 CrossProcessCompositorParent::AllocPLayerTransactionParent(const nsTArray<LayersBackend>&,
                                                            const uint64_t& aId,
                                                            TextureFactoryIdentifier* aTextureFactoryIdentifier,
                                                            bool *aSuccess)
 {
   MOZ_ASSERT(aId != 0);
 
-  if (sIndirectLayerTrees[aId].mParent) {
-    LayerManagerComposite* lm = sIndirectLayerTrees[aId].mParent->GetLayerManager();
+  if (sIndirectLayerTrees[aId].mLayerManager) {
+    LayerManagerComposite* lm = sIndirectLayerTrees[aId].mLayerManager;
     *aTextureFactoryIdentifier = lm->GetTextureFactoryIdentifier();
     *aSuccess = true;
     LayerTransactionParent* p = new LayerTransactionParent(lm, this, aId);
     p->AddIPDLReference();
     return p;
   }
 
   NS_WARNING("Created child without a matching parent?");

--- a/gfx/layers/ipc/CompositorParent.h
+++ b/gfx/layers/ipc/CompositorParent.h
@@ -102,18 +102,16 @@ public:
    * be called by the widget code when it loses its viewport information
    * (or for whatever reason wants to refresh the viewport information).
    * The information refresh happens because the compositor will call
    * SetFirstPaintViewport on the next frame of composition.
    */
   void ForceIsFirstPaint();
   void Destroy();
 
-  LayerManagerComposite* GetLayerManager() { return mLayerManager; }
-
   void NotifyChildCreated(uint64_t aChild);
 
   void AsyncRender();
 
   // Can be called from any thread
   void ScheduleRenderOnCompositorThread();
   void SchedulePauseOnCompositorThread();
   /**
@@ -198,16 +196,17 @@ public:
   static void StartUpWithExistingThread(MessageLoop* aMsgLoop,
                                         PlatformThreadId aThreadID);
 
   struct LayerTreeState {
     LayerTreeState();
     nsRefPtr<Layer> mRoot;
     nsRefPtr<GeckoContentController> mController;
     CompositorParent* mParent;
+    LayerManagerComposite* mLayerManager;
     TargetConfig mTargetConfig;
   };
 
   /**
    * Lookup the indirect shadow tree for |aId| and return it if it
    * exists.  Otherwise null is returned.  This must only be called on
    * the compositor thread.
    */

--- a/gfx/layers/moz.build
+++ b/gfx/layers/moz.build
@@ -123,17 +123,16 @@ EXPORTS.mozilla.layers += [
     'D3D9SurfaceImage.h',
     'Effects.h',
     'ImageDataSerializer.h',
     'ipc/AsyncPanZoomController.h',
     'ipc/Axis.h',
     'ipc/CompositableForwarder.h',
     'ipc/CompositableTransactionParent.h',
     'ipc/CompositorChild.h',
-    'ipc/CompositorCocoaWidgetHelper.h',
     'ipc/CompositorParent.h',
     'ipc/GeckoContentController.h',
     'ipc/GestureEventListener.h',
     'ipc/ImageBridgeChild.h',
     'ipc/ImageBridgeParent.h',
     'ipc/ISurfaceAllocator.h',
     'ipc/LayerTransactionChild.h',
     'ipc/LayerTransactionParent.h',
@@ -235,17 +234,16 @@ UNIFIED_SOURCES += [
     'CopyableCanvasLayer.cpp',
     'Effects.cpp',
     'ImageDataSerializer.cpp',
     'ImageLayers.cpp',
     'ipc/AsyncPanZoomController.cpp',
     'ipc/Axis.cpp',
     'ipc/CompositableTransactionParent.cpp',
     'ipc/CompositorChild.cpp',
-    'ipc/CompositorCocoaWidgetHelper.cpp',
     'ipc/CompositorParent.cpp',
     'ipc/GestureEventListener.cpp',
     'ipc/ImageBridgeChild.cpp',
     'ipc/ImageBridgeParent.cpp',
     'ipc/ISurfaceAllocator.cpp',
     'ipc/LayerTransactionChild.cpp',
     'ipc/LayerTransactionParent.cpp',
     'ipc/ShadowLayerChild.cpp',

--- a/widget/cocoa/nsChildView.mm
+++ b/widget/cocoa/nsChildView.mm
@@ -58,17 +58,16 @@
 #include "Layers.h"
 #include "ClientLayerManager.h"
 #include "mozilla/layers/LayerManagerComposite.h"
 #include "GLTextureImage.h"
 #include "GLContextProvider.h"
 #include "GLContext.h"
 #include "GLUploadHelpers.h"
 #include "mozilla/layers/GLManager.h"
-#include "mozilla/layers/CompositorCocoaWidgetHelper.h"
 #include "mozilla/layers/CompositorOGL.h"
 #include "mozilla/layers/BasicCompositor.h"
 #include "gfxUtils.h"
 #include "mozilla/gfx/2D.h"
 #include "mozilla/gfx/BorrowedContext.h"
 #ifdef ACCESSIBILITY
 #include "nsAccessibilityService.h"
 #include "mozilla/a11y/Platform.h"