Revert 160631 - [cc] Store CCLayerImpls as scoped_ptrs

cc/CCLayerTreeHostImpl.h

Index: cc/CCLayerTreeHostImpl.h
===================================================================
--- cc/CCLayerTreeHostImpl.h	(revision 160631)
+++ cc/CCLayerTreeHostImpl.h	(working copy)
@@ -123,7 +123,7 @@
 
     void readback(void* pixels, const IntRect&);
 
-    void setRootLayer(scoped_ptr<CCLayerImpl>);
+    void setRootLayer(PassOwnPtr<CCLayerImpl>);
     CCLayerImpl* rootLayer() { return m_rootLayerImpl.get(); }
 
     void setHudLayer(CCHeadsUpDisplayLayerImpl* layerImpl) { m_hudLayerImpl = layerImpl; }
@@ -131,7 +131,7 @@
 
     // Release ownership of the current layer tree and replace it with an empty
     // tree. Returns the root layer of the detached tree.
-    scoped_ptr<CCLayerImpl> detachLayerTree();
+    PassOwnPtr<CCLayerImpl> detachLayerTree();
 
     CCLayerImpl* rootScrollLayer() const { return m_rootScrollLayerImpl; }
 
@@ -253,7 +253,7 @@
     scoped_ptr<CCGraphicsContext> m_context;
     OwnPtr<CCResourceProvider> m_resourceProvider;
     OwnPtr<CCRenderer> m_renderer;
-    scoped_ptr<CCLayerImpl> m_rootLayerImpl;
+    OwnPtr<CCLayerImpl> m_rootLayerImpl;
     CCLayerImpl* m_rootScrollLayerImpl;
     CCLayerImpl* m_currentlyScrollingLayerImpl;
     CCHeadsUpDisplayLayerImpl* m_hudLayerImpl;