Improvements to uses of base::SmallMap

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 45 matching lines @@
 };
 
 struct TileMapKey {
   TileMapKey(int x, int y) : index_x(x), index_y(y) {}
   explicit TileMapKey(const std::pair<int, int>& index)
       : index_x(index.first), index_y(index.second) {}
 
   bool operator==(const TileMapKey& other) const {
     return index_x == other.index_x && index_y == other.index_y;
   }
+  bool operator<(const TileMapKey& other) const {
+    return std::tie(index_x, index_y) < std::tie(other.index_x, other.index_y);
+  }
 
   int index_x;
   int index_y;
 };
 
 struct TileMapKeyHash {
   size_t operator()(const TileMapKey& key) const {
     uint16_t value1 = static_cast<uint16_t>(key.index_x);
     uint16_t value2 = static_cast<uint16_t>(key.index_y);
     uint32_t value1_32 = value1;
@@ skipping 305 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_