cc: Ensure to skip the first tile that would be returned by twin.

cc/resources/raster_tile_priority_queue.h

 // Copyright 2014 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_RESOURCES_RASTER_TILE_PRIORITY_QUEUE_H_
 #define CC_RESOURCES_RASTER_TILE_PRIORITY_QUEUE_H_
 
 #include <set>
 #include <utility>
 #include <vector>
@@ skipping 10 matching lines @@
     PairedPictureLayerQueue();
     PairedPictureLayerQueue(const PictureLayerImpl::Pair& layer_pair,
                             TreePriority tree_priority);
     ~PairedPictureLayerQueue();
 
     bool IsEmpty() const;
     Tile* Top(TreePriority tree_priority);
     void Pop(TreePriority tree_priority);
 
     WhichTree NextTileIteratorTree(TreePriority tree_priority) const;
+    void SkipTilesReturnedByTwin(TreePriority tree_priority);
 
     PictureLayerImpl::LayerRasterTileIterator active_iterator;
     PictureLayerImpl::LayerRasterTileIterator pending_iterator;
     bool has_both_layers;
 
     // Set of returned tiles (excluding the current one) for DCHECKing.
     std::set<const Tile*> returned_tiles_for_debug;
   };
 
   RasterTilePriorityQueue();
@@ skipping 13 matching lines @@
   // objects directly (ie std::vector<PairedPictureLayerQueue>.
   ScopedPtrVector<PairedPictureLayerQueue> paired_queues_;
   TreePriority tree_priority_;
 
   DISALLOW_COPY_AND_ASSIGN(RasterTilePriorityQueue);
 };
 
 }  // namespace cc
 
 #endif  // CC_RESOURCES_RASTER_TILE_PRIORITY_QUEUE_H_