cc: Support mask layers in impl-side painting

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"
@@ skipping 34 matching lines @@
       const gfx::Transform& current_screen_transform,
       double time_delta);
 
   // For a given rect, iterates through tiles that can fill it.  If no
   // set of tiles with resources can fill the rect, then it will iterate
   // through null tiles with valid geometry_rect() until the rect is full.
   // If all tiles have resources, the union of all geometry_rects will
   // exactly fill rect with no overlap.
   class CC_EXPORT Iterator {
    public:
-    Iterator(PictureLayerTilingSet* set, float contents_scale, gfx::Rect rect);
+    Iterator(
+      const PictureLayerTilingSet* set,
+      float contents_scale,
+      gfx::Rect rect);
     ~Iterator();
 
     // Visible rect (no borders), always in the space of rect,
     // regardless of the relative contents scale of the tiling.
     gfx::Rect geometry_rect() const;
     // Texture rect (in texels) for geometry_rect
     gfx::RectF texture_rect() const;
     // Texture size in texels
     gfx::Size texture_size() const;
 
     Tile* operator->() const;
     Tile* operator*() const;
 
     Iterator& operator++();
     operator bool() const;
 
    private:
-    PictureLayerTilingSet* set_;
+    const PictureLayerTilingSet* set_;
     float contents_scale_;
     PictureLayerTiling::Iterator tiling_iter_;
     int current_tiling_;
 
     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_