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

cc/animation/layer_animation_controller.h

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_ANIMATION_LAYER_ANIMATION_CONTROLLER_H_
 #define CC_ANIMATION_LAYER_ANIMATION_CONTROLLER_H_
 
 #include "base/basictypes.h"
 #include "base/containers/hash_tables.h"
 #include "base/memory/ref_counted.h"
@@ skipping 128 matching lines @@
 
   enum UpdateActivationType {
     NormalActivation,
     ForceActivation
   };
   void UpdateActivation(UpdateActivationType type);
 
   void NotifyObserversOpacityAnimated(float opacity);
   void NotifyObserversTransformAnimated(const gfx::Transform& transform);
   void NotifyObserversFilterAnimated(const FilterOperations& filter);
-  void NotifyObserversScrollOffsetAnimated(gfx::Vector2dF scroll_offset);
+  void NotifyObserversScrollOffsetAnimated(const gfx::Vector2dF& scroll_offset);
 
   void NotifyObserversAnimationWaitingForDeletion();
 
   bool HasValueObserver();
   bool HasActiveValueObserver();
 
   AnimationRegistrar* registrar_;
   int id_;
   ScopedPtrVector<Animation> active_animations_;
 
   // This is used to ensure that we don't spam the registrar.
   bool is_active_;
 
   double last_tick_time_;
 
   ObserverList<LayerAnimationValueObserver> value_observers_;
   ObserverList<LayerAnimationEventObserver> event_observers_;
 
   LayerAnimationValueProvider* value_provider_;
 
   AnimationDelegate* layer_animation_delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerAnimationController);
 };
 
 }  // namespace cc
 
 #endif  // CC_ANIMATION_LAYER_ANIMATION_CONTROLLER_H_