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

cc/quads/checkerboard_draw_quad.h

Index: cc/quads/checkerboard_draw_quad.h
diff --git a/cc/quads/checkerboard_draw_quad.h b/cc/quads/checkerboard_draw_quad.h
index 4f7452eb0a6b620a1aaf12cc7c0789dae1e87c5b..ffa016f3adf5cf0520a0f465062b9e619e3bbf25 100644
--- a/cc/quads/checkerboard_draw_quad.h
+++ b/cc/quads/checkerboard_draw_quad.h
@@ -17,13 +17,13 @@ class CC_EXPORT CheckerboardDrawQuad : public DrawQuad {
   static scoped_ptr<CheckerboardDrawQuad> Create();
 
   void SetNew(const SharedQuadState* shared_quad_state,
-              gfx::Rect rect,
+              const gfx::Rect& rect,
               SkColor color);
 
   void SetAll(const SharedQuadState* shared_quad_state,
-              gfx::Rect rect,
-              gfx::Rect opaque_rect,
-              gfx::Rect visible_rect,
+              const gfx::Rect& rect,
+              const gfx::Rect& opaque_rect,
+              const gfx::Rect& visible_rect,
               bool needs_blending,
               SkColor color);