cc: Invalidate the full tiled layer when contents scale changes.

cc/contents_scaling_layer.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_CONTENTS_SCALING_LAYER_H_
 #define CC_CONTENTS_SCALING_LAYER_H_
 
 #include "cc/cc_export.h"
 #include "cc/layer.h"
 
 namespace cc {
 
 // Base class for layers that need contents scale.
 // The content bounds are determined by bounds and scale of the contents.
 class CC_EXPORT ContentsScalingLayer : public Layer {
  public:
   virtual void calculateContentsScale(
       float ideal_contents_scale,
       float* contents_scale_x,
       float* contents_scale_y,
       gfx::Size* content_bounds) OVERRIDE;
   virtual void didUpdateBounds() OVERRIDE;
 
+  virtual void update(
+    ResourceUpdateQueue& queue,
+    const OcclusionTracker* occlusion,
+    RenderingStats& stats) OVERRIDE;
+
  protected:
   ContentsScalingLayer();
   virtual ~ContentsScalingLayer();
 
   gfx::Size computeContentBoundsForScale(float scaleX, float scaleY) const;
+
+ private:
+  float last_update_contents_scale_x_;
+  float last_update_contents_scale_y_;
 };
 
 }  // namespace cc
 
 #endif  // CC_CONTENTS_SCALING_LAYER_H__