Make scrollAnimatorEnabled work on Mac like it does on other platforms

ui/gfx/animation/animation.h

 // Copyright (c) 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 UI_GFX_ANIMATION_ANIMATION_H_
 #define UI_GFX_ANIMATION_ANIMATION_H_
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
@@ skipping 46 matching lines @@
 
   bool is_animating() const { return is_animating_; }
 
   base::TimeDelta timer_interval() const { return timer_interval_; }
 
   // Returns true if rich animations should be rendered.
   // Looks at session type (e.g. remote desktop) and accessibility settings
   // to give guidance for heavy animations such as "start download" arrow.
   static bool ShouldRenderRichAnimation();
 
+  // Determines on a per-platform basis whether scroll animations
+  // (e.g. produced by home/end key) should be enabled.
+  static bool ScrollAnimationsEnabledBySystem();
+
  protected:
   // Invoked from Start to allow subclasses to prepare for the animation.
   virtual void AnimationStarted() {}
 
   // Invoked from Stop after we're removed from the container but before the
   // delegate has been invoked.
   virtual void AnimationStopped() {}
 
   // Invoked from stop to determine if cancel should be invoked. If this returns
   // true the delegate is notified the animation was canceled, otherwise the
@@ skipping 24 matching lines @@
 
   // Time we started at.
   base::TimeTicks start_time_;
 
   DISALLOW_COPY_AND_ASSIGN(Animation);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_ANIMATION_ANIMATION_H_