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

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index 9063caf66d67f57c2dad462ec1ec9320663c8369..146c0e03a751f13812539c67adb2341dabdd1a64 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -1899,7 +1899,7 @@ void LayerTreeHostImpl::ReleaseGL() {
   client_->SetNeedsCommitOnImplThread();
 }
 
-void LayerTreeHostImpl::SetViewportSize(gfx::Size device_viewport_size) {
+void LayerTreeHostImpl::SetViewportSize(const gfx::Size& device_viewport_size) {
   if (device_viewport_size == device_viewport_size_)
     return;
 
@@ -1925,7 +1925,7 @@ void LayerTreeHostImpl::SetOverdrawBottomHeight(float overdraw_bottom_height) {
 
 void LayerTreeHostImpl::SetOverhangUIResource(
     UIResourceId overhang_ui_resource_id,
-    gfx::Size overhang_ui_resource_size) {
+    const gfx::Size& overhang_ui_resource_size) {
   overhang_ui_resource_id_ = overhang_ui_resource_id;
   overhang_ui_resource_size_ = overhang_ui_resource_size;
 }