[#7] Pass gfx structs by const ref (gfx::Size)

cc/layers/delegated_renderer_layer.cc

Index: cc/layers/delegated_renderer_layer.cc
diff --git a/cc/layers/delegated_renderer_layer.cc b/cc/layers/delegated_renderer_layer.cc
index 6616b9b345a48f1063d87acc264e21f2162de143..aaee787c5e8ccaee97e9319ac5f481caea3dcb58 100644
--- a/cc/layers/delegated_renderer_layer.cc
+++ b/cc/layers/delegated_renderer_layer.cc
@@ -86,7 +86,7 @@ void DelegatedRendererLayer::ProviderHasNewFrame() {
   SetNextCommitWaitsForActivation();
 }
 
-void DelegatedRendererLayer::SetDisplaySize(gfx::Size size) {
+void DelegatedRendererLayer::SetDisplaySize(const gfx::Size& size) {
   if (display_size_ == size)
     return;
   display_size_ = size;