[#5] Pass gfx structs by const ref (gfx::Vector2dF)

cc/test/animation_test_common.h

Index: cc/test/animation_test_common.h
diff --git a/cc/test/animation_test_common.h b/cc/test/animation_test_common.h
index 1205bf30929cc90c93e0d4be2bb0f7de66f70fdc..e23be0b6714c8950c7c4b088982e4c3cb3ef0536 100644
--- a/cc/test/animation_test_common.h
+++ b/cc/test/animation_test_common.h
@@ -75,7 +75,8 @@ class FakeLayerAnimationValueObserver : public LayerAnimationValueObserver {
   virtual void OnFilterAnimated(const FilterOperations& filters) OVERRIDE;
   virtual void OnOpacityAnimated(float opacity) OVERRIDE;
   virtual void OnTransformAnimated(const gfx::Transform& transform) OVERRIDE;
-  virtual void OnScrollOffsetAnimated(gfx::Vector2dF scroll_offset) OVERRIDE;
+  virtual void OnScrollOffsetAnimated(
+      const gfx::Vector2dF& scroll_offset) OVERRIDE;
   virtual void OnAnimationWaitingForDeletion() OVERRIDE;
   virtual bool IsActive() const OVERRIDE;
 
@@ -106,7 +107,7 @@ class FakeLayerAnimationValueProvider : public LayerAnimationValueProvider {
  public:
   virtual gfx::Vector2dF ScrollOffsetForAnimation() const OVERRIDE;
 
-  void set_scroll_offset(gfx::Vector2dF scroll_offset) {
+  void set_scroll_offset(const gfx::Vector2dF& scroll_offset) {
     scroll_offset_ = scroll_offset;
   }