cc: Optimize OnePriorityRectIterator a little bit.

cc/tiles/tiling_set_raster_queue_all.h

Index: cc/tiles/tiling_set_raster_queue_all.h
diff --git a/cc/tiles/tiling_set_raster_queue_all.h b/cc/tiles/tiling_set_raster_queue_all.h
index 62d2249373046fcc10bdf06b198211b396bd5e66..951f9393da22df0a640d89c6c0ba66a2eee2cee2 100644
--- a/cc/tiles/tiling_set_raster_queue_all.h
+++ b/cc/tiles/tiling_set_raster_queue_all.h
@@ -41,7 +41,7 @@ class CC_EXPORT TilingSetRasterQueueAll {
 
    protected:
     ~OnePriorityRectIterator() = default;
-    bool TileNeedsRaster(Tile* tile) const {
+    bool TileNeedsRaster(const Tile* tile) const {
       return tile->draw_info().NeedsRaster() && !tiling_->IsTileOccluded(tile);
     }
 
@@ -49,6 +49,7 @@ class CC_EXPORT TilingSetRasterQueueAll {
     void AdvanceToNextTile(TilingIteratorType* iterator);
     template <typename TilingIteratorType>
     bool GetFirstTileAndCheckIfValid(TilingIteratorType* iterator);
+    bool IsTileValid(const Tile* tile) const;
 
     PrioritizedTile current_tile_;
     PictureLayerTiling* tiling_;