cc: Fix const value pattern by replacing it by non-const or reference.

cc/tiles/prioritized_tile.h

 // Copyright 2015 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_PRIORITIZED_TILE_H_
 #define CC_TILES_PRIORITIZED_TILE_H_
 
 #include "cc/base/cc_export.h"
 #include "cc/playback/raster_source.h"
 #include "cc/tiles/picture_layer_tiling.h"
 #include "cc/tiles/tile.h"
 #include "cc/tiles/tile_priority.h"
 
 namespace cc {
 class RasterSource;
 class PictureLayerTiling;
 
 class CC_EXPORT PrioritizedTile {
  public:
   // This class is constructed and returned by a |PictureLayerTiling|, and
   // represents a tile and its priority.
   PrioritizedTile();
   PrioritizedTile(Tile* tile,
                   const PictureLayerTiling* source_tiling,
-                  const TilePriority priority,
+                  const TilePriority& priority,
                   bool is_occluded,
                   bool is_process_for_images_only);
   ~PrioritizedTile();
 
   Tile* tile() const { return tile_; }
   const scoped_refptr<RasterSource>& raster_source() const {
     return source_tiling_->raster_source();
   }
   const TilePriority& priority() const { return priority_; }
   bool is_occluded() const { return is_occluded_; }
   bool is_process_for_images_only() const {
     return is_process_for_images_only_;
   }
 
   void AsValueInto(base::trace_event::TracedValue* value) const;
 
  private:
   Tile* tile_ = nullptr;
   const PictureLayerTiling* source_tiling_ = nullptr;
   TilePriority priority_;
   bool is_occluded_ = false;
   bool is_process_for_images_only_ = false;
 };
 
 }  // namespace cc
 
 #endif  // CC_TILES_PRIORITIZED_TILE_H_