cc: Add PictureLayerTilingSet to manage PictureLayerTiling

cc/picture_layer_impl.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_IMPL_H_
 #define CC_PICTURE_LAYER_IMPL_H_
 
 #include "cc/layer_impl.h"
 #include "cc/picture_layer_tiling.h"
+#include "cc/picture_layer_tiling_set.h"
 #include "cc/picture_pile.h"
 #include "cc/scoped_ptr_vector.h"
 
 namespace cc {
 
 struct AppendQuadsData;
 class QuadSink;
 
 class CC_EXPORT PictureLayerImpl : public LayerImpl,
                                    public PictureLayerTilingClient {
@@ skipping 15 matching lines @@
 
   // PushPropertiesTo active tree => pending tree
   void SyncFromActiveLayer(const PictureLayerImpl* other);
 
   // Called post-calcDraw.
   void Update();
 
 protected:
   PictureLayerImpl(int id);
 
-  ScopedPtrVector<PictureLayerTiling> tilings_;
+  PictureLayerTilingSet tilings_;
   PicturePile pile_;
 
   friend class PictureLayer;
   DISALLOW_COPY_AND_ASSIGN(PictureLayerImpl);
 };
 
 }
 
 #endif  // CC_PICTURE_LAYER_IMPL_H_