Use a bitfield to store animatable properties.

ash/rotator/screen_rotation.h

 // Copyright (c) 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 ASH_SCREEN_ROTATION_H_
 #define ASH_SCREEN_ROTATION_H_
 
 #include "ash/ash_export.h"
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 27 matching lines @@
   // animation.
   void InitTransform(ui::Layer* layer);
 
   // Implementation of ui::LayerAnimationDelegate
   virtual void OnStart(ui::LayerAnimationDelegate* delegate) OVERRIDE;
   virtual bool OnProgress(double t,
                           ui::LayerAnimationDelegate* delegate) OVERRIDE;
   virtual void OnGetTarget(TargetValue* target) const OVERRIDE;
   virtual void OnAbort(ui::LayerAnimationDelegate* delegate) OVERRIDE;
 
-  static const ui::LayerAnimationElement::AnimatableProperties&
-      GetProperties();
-
   scoped_ptr<ui::InterpolatedTransform> interpolated_transform_;
 
   // The number of degrees to rotate.
   int degrees_;
 
   // The target origin.
   gfx::Point new_origin_;
 
   DISALLOW_COPY_AND_ASSIGN(ScreenRotation);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SCREEN_ROTATION_H_