cc: Only create tilings for layers that draws content.

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 30 matching lines @@
     tilings_[i]->Invalidate(invalidation);
 }
 
 void PictureLayerTilingSet::AddTiling(float contents_scale,
                                       gfx::Size tile_size) {
   tilings_.append(PictureLayerTiling::Create(contents_scale, tile_size));
   tilings_.last()->SetClient(client_);
   tilings_.last()->SetLayerBounds(layer_bounds_);
 }
 
+void PictureLayerTilingSet::Reset() {
+  for (size_t i = 0; i < tilings_.size(); ++i)
+    tilings_[i]->Reset();
+}
+
 PictureLayerTilingSet::Iterator::Iterator(PictureLayerTilingSet* set,
                                           float contents_scale,
                                           gfx::Rect content_rect)
     : set_(set),
       contents_scale_(contents_scale),
       current_tiling_(-1) {
   missing_region_.Union(content_rect);
   ++(*this);
 }
 
@@ skipping 104 matching lines @@
     const gfx::Transform& current_screen_transform,
     double time_delta) {
   for (size_t i = 0; i < tilings_.size(); ++i) {
     tilings_[i]->UpdateTilePriorities(
         device_viewport, layer_content_scale_x, layer_content_scale_y,
         last_screen_transform, current_screen_transform, time_delta);
   }
 }
 
 }  // namespace cc