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

cc/layers/io_surface_layer.cc

Index: cc/layers/io_surface_layer.cc
diff --git a/cc/layers/io_surface_layer.cc b/cc/layers/io_surface_layer.cc
index 209827da73dbb66519cf86313f070e7afb7e1f6b..1e945150a0c329eaf1e38900abe28307287fb6ba 100644
--- a/cc/layers/io_surface_layer.cc
+++ b/cc/layers/io_surface_layer.cc
@@ -17,7 +17,7 @@
 IOSurfaceLayer::~IOSurfaceLayer() {}
 
 void IOSurfaceLayer::SetIOSurfaceProperties(uint32_t io_surface_id,
-                                            const gfx::Size& size) {
+                                            gfx::Size size) {
   io_surface_id_ = io_surface_id;
   io_surface_size_ = size;
   SetNeedsCommit();