cc: Optimize OnePriorityRectIterator a little bit.

cc/tiles/tiling_set_raster_queue_all.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_TILES_TILING_SET_RASTER_QUEUE_ALL_H_
 #define CC_TILES_TILING_SET_RASTER_QUEUE_ALL_H_
 
 #include "base/containers/stack_container.h"
 #include "cc/base/cc_export.h"
 #include "cc/tiles/picture_layer_tiling_set.h"
@@ skipping 23 matching lines @@
     OnePriorityRectIterator(
         PictureLayerTiling* tiling,
         TilingData* tiling_data,
         PictureLayerTiling::PriorityRectType priority_rect_type);
 
     bool done() const { return !current_tile_.tile(); }
     const PrioritizedTile& operator*() const { return current_tile_; }
 
    protected:
     ~OnePriorityRectIterator() = default;
-    bool TileNeedsRaster(Tile* tile) const {
+    bool TileNeedsRaster(const Tile* tile) const {
       return tile->draw_info().NeedsRaster() && !tiling_->IsTileOccluded(tile);
     }
 
     template <typename TilingIteratorType>
     void AdvanceToNextTile(TilingIteratorType* iterator);
     template <typename TilingIteratorType>
     bool GetFirstTileAndCheckIfValid(TilingIteratorType* iterator);
+    bool IsTileValid(const Tile* tile) const;
 
     PrioritizedTile current_tile_;
     PictureLayerTiling* tiling_;
     TilingData* tiling_data_;
     PictureLayerTiling::PriorityRectType priority_rect_type_;
   };
 
   // Iterates over visible rect only, left to right top to bottom order.
   class VisibleTilingIterator : public OnePriorityRectIterator {
    public:
@@ skipping 128 matching lines @@
   // ideal pending high res.
   base::StackVector<IterationStage, 6> stages_;
   TilingIterator iterators_[NUM_ITERATORS];
 
   DISALLOW_COPY_AND_ASSIGN(TilingSetRasterQueueAll);
 };
 
 }  // namespace cc
 
 #endif  // CC_TILES_TILING_SET_RASTER_QUEUE_ALL_H_