Activate LayerImpl tree with sync+push instead of pointer swap

cc/layer_tree_host_impl.h

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_LAYER_TREE_HOST_IMPL_H_
 #define CC_LAYER_TREE_HOST_IMPL_H_
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/time.h"
@@ skipping 293 matching lines @@
     void dumpRenderSurfaces(std::string*, int indent, const LayerImpl*) const;
 
     static LayerImpl* getNonCompositedContentLayerRecursive(LayerImpl* layer);
 
     scoped_ptr<OutputSurface> m_outputSurface;
     scoped_ptr<ResourceProvider> m_resourceProvider;
     scoped_ptr<Renderer> m_renderer;
     scoped_ptr<TileManager> m_tileManager;
 
     scoped_ptr<LayerTreeImpl> m_pendingTree;
+    scoped_ptr<LayerTreeImpl> m_recycleTree;

[enne (OOO), 2013/01/17 23:34:55]

Can you add some comment here about how all these trees work?

[jamesr, 2013/01/18 01:16:42]

Done.

     scoped_ptr<LayerTreeImpl> m_activeTree;
 
     bool m_scrollDeltaIsInViewportSpace;
     LayerTreeSettings m_settings;
     LayerTreeDebugState m_debugState;
     gfx::Size m_layoutViewportSize;
     gfx::Size m_deviceViewportSize;
     float m_deviceScaleFactor;
     bool m_visible;
     bool m_contentsTexturesPurged;
@@ skipping 28 matching lines @@
     size_t m_lastSentMemoryUseBytes;
 
     scoped_ptr<AnimationRegistrar> m_animationRegistrar;
 
     DISALLOW_COPY_AND_ASSIGN(LayerTreeHostImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYER_TREE_HOST_IMPL_H_