[#2] Pass gfx structs by const ref (gfx::Rect, gfx::RectF)

cc/resources/layer_tiling_data.cc

Index: cc/resources/layer_tiling_data.cc
diff --git a/cc/resources/layer_tiling_data.cc b/cc/resources/layer_tiling_data.cc
index 6b332341b8f490f059c3d4c481ac810d69ed5dee..e9caf9bb5fc28aa934d2312c55fc923603a518e2 100644
--- a/cc/resources/layer_tiling_data.cc
+++ b/cc/resources/layer_tiling_data.cc
@@ -66,7 +66,7 @@ LayerTilingData::Tile* LayerTilingData::TileAt(int i, int j) const {
   return tiles_.get(std::make_pair(i, j));
 }
 
-void LayerTilingData::ContentRectToTileIndices(gfx::Rect content_rect,
+void LayerTilingData::ContentRectToTileIndices(const gfx::Rect& content_rect,
                                                int* left,
                                                int* top,
                                                int* right,
@@ -90,7 +90,7 @@ gfx::Rect LayerTilingData::TileRect(const Tile* tile) const {
 }
 
 Region LayerTilingData::OpaqueRegionInContentRect(
-    gfx::Rect content_rect) const {
+    const gfx::Rect& content_rect) const {
   if (content_rect.IsEmpty())
     return Region();