--- a/gfx/layers/ipc/ShadowLayersParent.cpp
+++ b/gfx/layers/ipc/ShadowLayersParent.cpp
@@ -320,17 +320,17 @@ ShadowLayersParent::RecvUpdate(const nsT
       }
       break;
     }
 
       // Tree ops
     case Edit::TOpSetRoot: {
       MOZ_LAYERS_LOG(("[ParentSide] SetRoot"));
 
-      mRoot = AsShadowLayer(edit.get_OpSetRoot())->AsLayer();
+      mRoot = AsShadowLayer(edit.get_OpSetRoot())->AsContainer();
       break;
     }
     case Edit::TOpInsertAfter: {
       MOZ_LAYERS_LOG(("[ParentSide] InsertAfter"));
 
       const OpInsertAfter& oia = edit.get_OpInsertAfter();
       ShadowContainer(oia)->AsContainer()->InsertAfter(
         ShadowChild(oia)->AsLayer(), ShadowAfter(oia)->AsLayer());

--- a/gfx/layers/ipc/ShadowLayersParent.h
+++ b/gfx/layers/ipc/ShadowLayersParent.h
@@ -61,30 +61,30 @@ class ShadowLayersParent : public PLayer
   typedef nsTArray<EditReply> EditReplyArray;
 
 public:
   ShadowLayersParent(ShadowLayerManager* aManager);
   ~ShadowLayersParent();
 
   ShadowLayerManager* layer_manager() const { return mLayerManager; }
 
-  Layer* GetRoot() const { return mRoot; }
+  ContainerLayer* GetRoot() const { return mRoot; }
 
 protected:
   NS_OVERRIDE virtual bool RecvUpdate(const EditArray& cset,
                                       EditReplyArray* reply);
 
   NS_OVERRIDE virtual PLayerParent* AllocPLayer();
   NS_OVERRIDE virtual bool DeallocPLayer(PLayerParent* actor);
 
 private:
   RenderFrameParent* Frame();
 
   nsRefPtr<ShadowLayerManager> mLayerManager;
   // Hold the root because it might be grafted under various
   // containers in the "real" layer tree
-  nsRefPtr<Layer> mRoot;
+  nsRefPtr<ContainerLayer> mRoot;
 };
 
 } // namespace layers
 } // namespace mozilla
 
 #endif // ifndef mozilla_layers_ShadowLayersParent_h

--- a/layout/base/FrameLayerBuilder.cpp
+++ b/layout/base/FrameLayerBuilder.cpp
@@ -1315,17 +1315,17 @@ SetHasContainerLayer(nsIFrame* aFrame)
   aFrame->AddStateBits(NS_FRAME_HAS_CONTAINER_LAYER);
   for (nsIFrame* f = aFrame;
        f && !(f->GetStateBits() & NS_FRAME_HAS_CONTAINER_LAYER_DESCENDANT);
        f = nsLayoutUtils::GetCrossDocParentFrame(f)) {
     f->AddStateBits(NS_FRAME_HAS_CONTAINER_LAYER_DESCENDANT);
   }
 }
 
-already_AddRefed<Layer>
+already_AddRefed<ContainerLayer>
 FrameLayerBuilder::BuildContainerLayerFor(nsDisplayListBuilder* aBuilder,
                                           LayerManager* aManager,
                                           nsIFrame* aContainerFrame,
                                           nsDisplayItem* aContainerItem,
                                           const nsDisplayList& aChildren)
 {
   FrameProperties props = aContainerFrame->Properties();
   PRUint32 containerDisplayItemKey =

--- a/layout/base/FrameLayerBuilder.h
+++ b/layout/base/FrameLayerBuilder.h
@@ -85,16 +85,17 @@ enum LayerState {
  * 
  * FrameLayerBuilder sets up ThebesLayers so that 0,0 in the Thebes layer
  * corresponds to the (pixel-snapped) top-left of the aActiveScrolledRoot.
  * It sets up ContainerLayers so that 0,0 in the container layer
  * corresponds to the snapped top-left of the display list reference frame.
  */
 class FrameLayerBuilder {
 public:
+  typedef layers::ContainerLayer ContainerLayer; 
   typedef layers::Layer Layer; 
   typedef layers::ThebesLayer ThebesLayer;
   typedef layers::LayerManager LayerManager;
 
   FrameLayerBuilder() :
     mRetainingManager(nsnull),
     mInvalidateAllThebesContent(PR_FALSE),
     mInvalidateAllLayers(PR_FALSE)
@@ -133,21 +134,22 @@ public:
    * This gets called by display list code. It calls BuildLayer on the
    * items in the display list, making items with their own layers
    * children of the new container, and assigning all other items to
    * ThebesLayer children created and managed by the FrameLayerBuilder.
    * Returns a layer with clip rect cleared; it is the
    * caller's responsibility to add any clip rect and set the visible
    * region.
    */
-  already_AddRefed<Layer> BuildContainerLayerFor(nsDisplayListBuilder* aBuilder,
-                                                 LayerManager* aManager,
-                                                 nsIFrame* aContainerFrame,
-                                                 nsDisplayItem* aContainerItem,
-                                                 const nsDisplayList& aChildren);
+  already_AddRefed<ContainerLayer>
+  BuildContainerLayerFor(nsDisplayListBuilder* aBuilder,
+                         LayerManager* aManager,
+                         nsIFrame* aContainerFrame,
+                         nsDisplayItem* aContainerItem,
+                         const nsDisplayList& aChildren);
 
   /**
    * Get a retained layer for a display item that needs to create its own
    * layer for rendering (i.e. under nsDisplayItem::BuildLayer). Returns
    * null if no retained layer is available, which usually means that this
    * display item didn't have a layer before so the caller will
    * need to create one.
    * Returns a layer with clip rect cleared; it is the

--- a/layout/base/nsDisplayList.cpp
+++ b/layout/base/nsDisplayList.cpp
@@ -398,17 +398,17 @@ void nsDisplayList::PaintForFrame(nsDisp
   }
 
   if (aCtx) {
     layerManager->BeginTransactionWithTarget(aCtx->ThebesContext());
   } else {
     layerManager->BeginTransaction();
   }
 
-  nsRefPtr<Layer> root = aBuilder->LayerBuilder()->
+  nsRefPtr<ContainerLayer> root = aBuilder->LayerBuilder()->
     BuildContainerLayerFor(aBuilder, layerManager, aForFrame, nsnull, *this);
   if (!root)
     return;
 
   nsIntRect visible =
     mVisibleRect.ToNearestPixels(aForFrame->PresContext()->AppUnitsPerDevPixel());
   root->SetVisibleRegion(nsIntRegion(visible));
 

--- a/layout/ipc/RenderFrameParent.cpp
+++ b/layout/ipc/RenderFrameParent.cpp
@@ -168,17 +168,17 @@ RenderFrameParent::BuildLayer(nsDisplayL
     // FIXME handle the former case somehow, probably with an API to
     // draw a manager's subtree.  The latter is bad bad bad, but the
     // the NS_ABORT_IF_FALSE() above will flag it.  Returning NULL
     // here will just cause the shadow subtree not to be rendered.
     return nsnull;
   }
 
   Layer* containerRoot = mContainer ? RootOf(mContainer) : nsnull;
-  Layer* shadowRoot = GetRootLayer();
+  ContainerLayer* shadowRoot = GetRootLayer();
   NS_ABORT_IF_FALSE(!shadowRoot || shadowRoot->Manager() == aManager,
                     "retaining manager changed out from under us ... HELP!");
 
   if (mContainer && shadowRoot != containerRoot) {
     // Shadow root changed.  Remove it from the container, if it
     // existed.
     if (containerRoot) {
       mContainer->RemoveChild(containerRoot);
@@ -258,17 +258,17 @@ RenderFrameParent::GetShadowLayers() con
 {
   const nsTArray<PLayersParent*>& shadowParents = ManagedPLayersParent();
   NS_ABORT_IF_FALSE(shadowParents.Length() <= 1,
                     "can only support at most 1 ShadowLayersParent");
   return (shadowParents.Length() == 1) ?
     static_cast<ShadowLayersParent*>(shadowParents[0]) : nsnull;
 }
 
-Layer*
+ContainerLayer*
 RenderFrameParent::GetRootLayer() const
 {
   ShadowLayersParent* shadowLayers = GetShadowLayers();
   return shadowLayers ? shadowLayers->GetRoot() : nsnull;
 }
 
 }  // namespace layout
 }  // namespace mozilla

--- a/layout/ipc/RenderFrameParent.h
+++ b/layout/ipc/RenderFrameParent.h
@@ -78,17 +78,17 @@ protected:
   NS_OVERRIDE void ActorDestroy(ActorDestroyReason why);
 
   NS_OVERRIDE virtual PLayersParent* AllocPLayers();
   NS_OVERRIDE virtual bool DeallocPLayers(PLayersParent* aLayers);
 
 private:
   LayerManager* GetLayerManager() const;
   ShadowLayersParent* GetShadowLayers() const;
-  Layer* GetRootLayer() const;
+  ContainerLayer* GetRootLayer() const;
 
   nsRefPtr<nsFrameLoader> mFrameLoader;
   nsRefPtr<ContainerLayer> mContainer;
 };
 
 } // namespace layout
 } // namespace mozilla