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

cc/base/math_util.h

Index: cc/base/math_util.h
diff --git a/cc/base/math_util.h b/cc/base/math_util.h
index fca08ef656e1e06c8e201294589cbb46a926a177..6cad1ad1c5a4022bcb6ecb9957adef4fecc93225 100644
--- a/cc/base/math_util.h
+++ b/cc/base/math_util.h
@@ -165,7 +165,7 @@
                                       const gfx::Vector2dF& destination);
 
   // Conversion to value.
-  static scoped_ptr<base::Value> AsValue(const gfx::Size& s);
+  static scoped_ptr<base::Value> AsValue(gfx::Size s);
   static scoped_ptr<base::Value> AsValue(const gfx::SizeF& s);
   static scoped_ptr<base::Value> AsValue(const gfx::Rect& r);
   static bool FromValue(const base::Value*, gfx::Rect* out_rect);