cc: Reset raster scale if we didn't sync high res tiling.

cc/resources/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_RESOURCES_PICTURE_LAYER_TILING_SET_H_
 #define CC_RESOURCES_PICTURE_LAYER_TILING_SET_H_
 
 #include "cc/base/region.h"
 #include "cc/base/scoped_ptr_vector.h"
 #include "cc/resources/picture_layer_tiling.h"
 #include "ui/gfx/size.h"
 
 namespace cc {
 
 class CC_EXPORT PictureLayerTilingSet {
  public:
   PictureLayerTilingSet(PictureLayerTilingClient* client,
                         const gfx::Size& layer_bounds);
   ~PictureLayerTilingSet();
 
   void SetClient(PictureLayerTilingClient* client);
   const PictureLayerTilingClient* client() const { return client_; }
 
   // Make this set of tilings match the same set of content scales from |other|.
   // Delete any tilings that don't meet |minimum_contents_scale|.  Recreate
   // any tiles that intersect |layer_invalidation|.  Update the size of all
   // tilings to |new_layer_bounds|.
-  void SyncTilings(
-     const PictureLayerTilingSet& other,
-     const gfx::Size& new_layer_bounds,
-     const Region& layer_invalidation,
-     float minimum_contents_scale);
+  // Returns true if we had at least one high res tiling synced.
+  bool SyncTilings(const PictureLayerTilingSet& other,
+                   const gfx::Size& new_layer_bounds,
+                   const Region& layer_invalidation,
+                   float minimum_contents_scale);
 
   void RemoveTilesInRegion(const Region& region);
 
   gfx::Size layer_bounds() const { return layer_bounds_; }
 
   void SetCanUseLCDText(bool can_use_lcd_text);
 
   PictureLayerTiling* AddTiling(float contents_scale);
   size_t num_tilings() const { return tilings_.size(); }
   int NumHighResTilings() const;
@@ skipping 73 matching lines @@
   gfx::Size layer_bounds_;
   ScopedPtrVector<PictureLayerTiling> tilings_;
 
   friend class Iterator;
   DISALLOW_COPY_AND_ASSIGN(PictureLayerTilingSet);
 };
 
 }  // namespace cc
 
 #endif  // CC_RESOURCES_PICTURE_LAYER_TILING_SET_H_