Activate LayerImpl tree with sync+push instead of pointer swap

cc/picture_layer_tiling_set.h

 // Copyright 2012 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_PICTURE_LAYER_TILING_SET_H_
 #define CC_PICTURE_LAYER_TILING_SET_H_
 
 #include "cc/picture_layer_tiling.h"
 #include "cc/region.h"
 #include "cc/scoped_ptr_vector.h"
 #include "ui/gfx/size.h"
 
 namespace cc {
 
 class CC_EXPORT PictureLayerTilingSet {
  public:
-  PictureLayerTilingSet(PictureLayerTilingClient* client);
+  explicit PictureLayerTilingSet(PictureLayerTilingClient* client);
   ~PictureLayerTilingSet();
 
+  void SetClient(PictureLayerTilingClient* client);
+
   // Shallow copies all data (except client and bounds from other).
   void CloneAll(
      const PictureLayerTilingSet& other,
      const Region& invalidation);
   void Clone(const PictureLayerTiling* tiling, const Region& invalidation);
 
   void SetLayerBounds(gfx::Size layer_bounds);
   gfx::Size LayerBounds() const;
 
   PictureLayerTiling* AddTiling(
@@ skipping 67 matching lines @@
 
     Region current_region_;
     Region missing_region_;
     Region::Iterator region_iter_;
   };
 
  private:
   PictureLayerTilingClient* client_;
   gfx::Size layer_bounds_;
   ScopedPtrVector<PictureLayerTiling> tilings_;
-  Region invalidation_;
 
   friend class Iterator;
 };
 
 }  // namespace cc
 
 #endif  // CC_PICTURE_LAYER_TILING_SET_H_