Allow task pools to reason about transparency.

cc/tiles/tile.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_TILES_TILE_H_
 #define CC_TILES_TILE_H_
 
 #include "base/memory/ref_counted.h"
 #include "cc/tiles/tile_draw_info.h"
 #include "ui/gfx/geometry/rect.h"
@@ skipping 25 matching lines @@
                const gfx::Rect& enclosing_layer_rect,
                const gfx::Rect& content_rect,
                float contents_scale)
         : tiling_i_index(tiling_i_index),
           tiling_j_index(tiling_j_index),
           enclosing_layer_rect(enclosing_layer_rect),
           content_rect(content_rect),
           contents_scale(contents_scale) {}
   };
 
-  enum TileRasterFlags { USE_PICTURE_ANALYSIS = 1 << 0 };
+  enum TileRasterFlags { USE_PICTURE_ANALYSIS = 1 << 0, IS_OPAQUE = 1 << 1 };
 
   typedef uint64 Id;
 
   Id id() const {
     return id_;
   }
 
   // TODO(vmpstr): Move this to the iterators.
   bool required_for_activation() const { return required_for_activation_; }
   void set_required_for_activation(bool is_required) {
     required_for_activation_ = is_required;
   }
   bool required_for_draw() const { return required_for_draw_; }
   void set_required_for_draw(bool is_required) {
     required_for_draw_ = is_required;
   }
 
   bool use_picture_analysis() const {
     return !!(flags_ & USE_PICTURE_ANALYSIS);
   }
 
+  bool is_opaque() const { return !!(flags_ & IS_OPAQUE); }
+
   void AsValueInto(base::trace_event::TracedValue* value) const;
 
   const TileDrawInfo& draw_info() const { return draw_info_; }
   TileDrawInfo& draw_info() { return draw_info_; }
 
   float contents_scale() const { return contents_scale_; }
   const gfx::Rect& content_rect() const { return content_rect_; }
   const gfx::Rect& enclosing_layer_rect() const {
     return enclosing_layer_rect_;
   }
@@ skipping 63 matching lines @@
   scoped_refptr<RasterTask> raster_task_;
 
   DISALLOW_COPY_AND_ASSIGN(Tile);
 };
 
 using ScopedTilePtr = scoped_ptr<Tile, Tile::Deleter>;
 
 }  // namespace cc
 
 #endif  // CC_TILES_TILE_H_