cc: Support mask layers in impl-side painting

cc/picture_layer_tiling_set.cc

 // 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.
 
 #include "cc/picture_layer_tiling_set.h"
 
 namespace cc {
 
 PictureLayerTilingSet::PictureLayerTilingSet(
     PictureLayerTilingClient * client)
@@ skipping 55 matching lines @@
   tilings_.last()->SetClient(client_);
   tilings_.last()->SetLayerBounds(layer_bounds_);
   return tilings_.last();
 }
 
 void PictureLayerTilingSet::Reset() {
   for (size_t i = 0; i < tilings_.size(); ++i)
     tilings_[i]->Reset();
 }
 
-PictureLayerTilingSet::Iterator::Iterator(PictureLayerTilingSet* set,
+PictureLayerTilingSet::Iterator::Iterator(const PictureLayerTilingSet* set,
                                           float contents_scale,
                                           gfx::Rect content_rect)
     : set_(set),
       contents_scale_(contents_scale),
       current_tiling_(-1) {
   missing_region_.Union(content_rect);
   ++(*this);
 }
 
 PictureLayerTilingSet::Iterator::~Iterator() {
@@ skipping 109 matching lines @@
         device_viewport,
         layer_content_scale_x,
         layer_content_scale_y,
         last_screen_transform,
         current_screen_transform,
         time_delta);
   }
 }
 
 }  // namespace cc