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

cc/input/page_scale_animation.h

 // Copyright 2011 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_INPUT_PAGE_SCALE_ANIMATION_H_
 #define CC_INPUT_PAGE_SCALE_ANIMATION_H_
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "ui/gfx/size.h"
 #include "ui/gfx/vector2d_f.h"
 
 namespace cc {
 class TimingFunction;
 
 // A small helper class that does the math for zoom animations, primarily for
 // double-tap zoom. Initialize it with starting and ending scroll/page scale
 // positions and an animation length time, then call ...AtTime() at every frame
 // to obtain the current interpolated position. The supplied timing function
 // is used to ease the animation.
 //
 // All sizes and vectors in this class's public methods are in the root scroll
 // layer's coordinate space.
 class PageScaleAnimation {
  public:
   // Construct with the state at the beginning of the animation.
   static scoped_ptr<PageScaleAnimation> Create(
-      gfx::Vector2dF start_scroll_offset,
+      const gfx::Vector2dF& start_scroll_offset,
       float start_page_scale_factor,
       const gfx::SizeF& viewport_size,
       const gfx::SizeF& root_layer_size,
       scoped_ptr<TimingFunction> timing_function);
 
   ~PageScaleAnimation();
 
   // The following methods initialize the animation. Call one of them
   // immediately after construction to set the final scroll and page scale.
 
   // Zoom while explicitly specifying the top-left scroll position.
-  void ZoomTo(gfx::Vector2dF target_scroll_offset,
+  void ZoomTo(const gfx::Vector2dF& target_scroll_offset,
               float target_page_scale_factor,
               double duration);
 
   // Zoom based on a specified anchor. The animator will attempt to keep it
   // at the same position on the physical display throughout the animation,
   // unless the edges of the root layer are hit. The anchor is specified
   // as an offset from the content layer.
-  void ZoomWithAnchor(gfx::Vector2dF anchor,
+  void ZoomWithAnchor(const gfx::Vector2dF& anchor,
                       float target_page_scale_factor,
                       double duration);
 
   // These should be called before the first frame of animation to initialize
   // the start time. StartAnimation should only be called once after creation.
   bool IsAnimationStarted() const;
   void StartAnimation(double time);
 
   // Call these functions while the animation is in progress to output the
   // current state.
   gfx::Vector2dF ScrollOffsetAtTime(double time) const;
   float PageScaleFactorAtTime(double time) const;
   bool IsAnimationCompleteAtTime(double time) const;
 
   // The following methods return state which is invariant throughout the
   // course of the animation.
   double start_time() const { return start_time_; }
   double duration() const { return duration_; }
   double end_time() const { return start_time_ + duration_; }
   gfx::Vector2dF target_scroll_offset() const { return target_scroll_offset_; }
   float target_page_scale_factor() const { return target_page_scale_factor_; }
 
  protected:
-  PageScaleAnimation(gfx::Vector2dF start_scroll_offset,
+  PageScaleAnimation(const gfx::Vector2dF& start_scroll_offset,
                      float start_page_scale_factor,
                      const gfx::SizeF& viewport_size,
                      const gfx::SizeF& root_layer_size,
                      scoped_ptr<TimingFunction> timing_function);
 
  private:
   void ClampTargetScrollOffset();
   void InferTargetScrollOffsetFromStartAnchor();
   void InferTargetAnchorFromScrollOffsets();
 
@@ skipping 21 matching lines @@
   double duration_;
 
   scoped_ptr<TimingFunction> timing_function_;
 
   DISALLOW_COPY_AND_ASSIGN(PageScaleAnimation);
 };
 
 }  // namespace cc
 
 #endif  // CC_INPUT_PAGE_SCALE_ANIMATION_H_