cc: Fix size_t to int truncations in tiles/ and trees/

cc/tiles/picture_layer_tiling_set.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_SET_H_
 #define CC_TILES_PICTURE_LAYER_TILING_SET_H_
 
 #include <set>
 #include <vector>
 
@@ skipping 134 matching lines @@
     Tile* operator->() const;
     Tile* operator*() const;
 
     CoverageIterator& operator++();
     operator bool() const;
 
     TileResolution resolution() const;
     PictureLayerTiling* CurrentTiling() const;
 
    private:
-    int NextTiling() const;
+    size_t NextTiling() const;
 
     const PictureLayerTilingSet* set_;
     float contents_scale_;
     float ideal_contents_scale_;
     PictureLayerTiling::CoverageIterator tiling_iter_;
-    int current_tiling_;
-    int ideal_tiling_;
+    size_t current_tiling_;
+    size_t ideal_tiling_;
 
     Region current_region_;
     Region missing_region_;
     Region::Iterator region_iter_;
   };
 
   void AsValueInto(base::trace_event::TracedValue* array) const;
   size_t GPUMemoryUsageInBytes() const;
 
   TilingRange GetTilingRange(TilingRangeType type) const;
@@ skipping 23 matching lines @@
   WhichTree tree_;
   PictureLayerTilingClient* client_;
 
   friend class Iterator;
   DISALLOW_COPY_AND_ASSIGN(PictureLayerTilingSet);
 };
 
 }  // namespace cc
 
 #endif  // CC_TILES_PICTURE_LAYER_TILING_SET_H_