cc: Always keep the PictureLayerImpl::twin_layer_ pointer valid.

cc/trees/layer_tree_host_impl.h

 // Copyright 2011 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_TREES_LAYER_TREE_HOST_IMPL_H_
 #define CC_TREES_LAYER_TREE_HOST_IMPL_H_
 
 #include <list>
 #include <set>
 #include <string>
@@ skipping 200 matching lines @@
   // When blocking, this prevents client_->NotifyReadyToActivate() from being
   // called. When disabled, it calls client_->NotifyReadyToActivate()
   // immediately if any notifications had been blocked while blocking.
   virtual void BlockNotifyReadyToActivateForTesting(bool block);
 
   // This allows us to inject DidInitializeVisibleTile events for testing.
   void DidInitializeVisibleTileForTesting();
 
   // Resets all of the trees to an empty state.
   void ResetTreesForTesting();
-  void ResetRecycleTreeForTesting();
 
   DrawMode GetDrawMode() const;
 
   // Viewport size in draw space: this size is in physical pixels and is used
   // for draw properties, tilings, quads and render passes.
   gfx::Size DrawViewportSize() const;
 
   // Viewport rect in view space used for tiling prioritization.
   const gfx::Rect ViewportRectForTilePriority() const;
 
@@ skipping 478 matching lines @@
   std::vector<PictureLayerImpl::Pair> picture_layer_pairs_;
 
   bool requires_high_res_to_draw_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHostImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_IMPL_H_