Improvements to uses of base::SmallMap

cc/tiles/picture_layer_tiling.cc

Index: cc/tiles/picture_layer_tiling.cc
diff --git a/cc/tiles/picture_layer_tiling.cc b/cc/tiles/picture_layer_tiling.cc
index 344cb32b6c04cc92ce00887c8862c30add532d73..fcd6ff2b69cb7621da29d56b09ec65403b335912 100644
--- a/cc/tiles/picture_layer_tiling.cc
+++ b/cc/tiles/picture_layer_tiling.cc
@@ -257,11 +257,11 @@ void PictureLayerTiling::RemoveTilesInRegion(const Region& layer_invalidation,
   // twin, so it's slated for removal in the future.
   if (live_tiles_rect_.IsEmpty())
     return;
-  // Pick 16 for the size of the SmallMap before it promotes to a unordered_map.
-  // 4x4 tiles should cover most small invalidations, and walking a vector of
-  // 16 is fast enough. If an invalidation is huge we will fall back to a
-  // unordered_map instead of a vector in the SmallMap.
-  base::SmallMap<std::unordered_map<TileMapKey, gfx::Rect, TileMapKeyHash>, 16>
+  // Pick 16 for the size of the small_map before it promotes to a
+  // unordered_map. 4x4 tiles should cover most small invalidations, and
+  // walking a vector of 16 is fast enough. If an invalidation is huge we will
+  // fall back to a unordered_map instead of a vector in the small_map.
+  base::small_map<std::unordered_map<TileMapKey, gfx::Rect, TileMapKeyHash>, 16>

[danakj, 2017/04/18 21:35:50]

This should be a flat_map too

       remove_tiles;
   gfx::Rect expanded_live_tiles_rect =
       tiling_data_.ExpandRectToTileBounds(live_tiles_rect_);