cc: Add checker-imaging support to TileManager.

cc/tiles/picture_layer_tiling.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_PICTURE_LAYER_TILING_H_
 #define CC_TILES_PICTURE_LAYER_TILING_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 117 matching lines @@
     return iter == tiles_.end() ? nullptr : iter->second.get();
   }
 
   bool has_tiles() const { return !tiles_.empty(); }
   // all_tiles_done() can return false negatives.
   bool all_tiles_done() const { return all_tiles_done_; }
   void set_all_tiles_done(bool all_tiles_done) {
     all_tiles_done_ = all_tiles_done;
   }
 
+  WhichTree tree() const { return tree_; }
+
   void VerifyNoTileNeedsRaster() const {
 #if DCHECK_IS_ON()
     for (const auto& tile_pair : tiles_) {
       DCHECK(!tile_pair.second->draw_info().NeedsRaster() ||
              IsTileOccluded(tile_pair.second.get()));
     }
 #endif  // DCHECK_IS_ON()
   }
 
   // For testing functionality.
@@ skipping 213 matching lines @@
   bool has_eventually_rect_tiles_ = false;
   bool all_tiles_done_ = true;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(PictureLayerTiling);
 };
 
 }  // namespace cc
 
 #endif  // CC_TILES_PICTURE_LAYER_TILING_H_