Explicit animation support

ui/base/animation/tween.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_BASE_ANIMATION_TWEEN_H_
 #define UI_BASE_ANIMATION_TWEEN_H_
 #pragma once
 
 #include "base/basictypes.h"
 #include "ui/base/ui_export.h"
 
 namespace gfx {
 class Rect;
 }
 
 namespace ui {
 
+class Transform;
+
 class UI_EXPORT Tween {
  public:
   enum Type {
     LINEAR,        // Linear.
     EASE_OUT,      // Fast in, slow out (default).
     EASE_IN,       // Slow in, fast out.
     EASE_IN_OUT,   // Slow in and out, fast in the middle.
     FAST_IN_OUT,   // Fast in and out, slow in the middle.
     EASE_OUT_SNAP, // Fast in, slow out, snap to final value.
     ZERO,          // Returns a value of 0 always.
   };
 
   // Returns the value based on the tween type. |state| is from 0-1.
   static double CalculateValue(Type type, double state);
 
   // Conveniences for getting a value between a start and end point.
   static double ValueBetween(double value, double start, double target);
   static int ValueBetween(double value, int start, int target);
   static gfx::Rect ValueBetween(double value,
                                 const gfx::Rect& start_bounds,
                                 const gfx::Rect& target_bounds);
+  static Transform ValueBetween(double value,
+                                const Transform& start_transform,
+                                const Transform& target_transform);
 
  private:
   Tween();
   ~Tween();
 
   DISALLOW_COPY_AND_ASSIGN(Tween);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_ANIMATION_TWEEN_H_