Gradient overlay for constrained window

ui/base/animation/linear_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_BASE_ANIMATION_LINEAR_ANIMATION_H_
 #define UI_BASE_ANIMATION_LINEAR_ANIMATION_H_
 
 #include "base/time.h"
 #include "ui/base/animation/animation.h"
 
@@ skipping 14 matching lines @@
   LinearAnimation(int frame_rate, AnimationDelegate* delegate);
 
   // Initializes all fields.
   LinearAnimation(int duration, int frame_rate, AnimationDelegate* delegate);
 
   // Gets the value for the current state, according to the animation curve in
   // use. This class provides only for a linear relationship, however subclasses
   // can override this to provide others.
   virtual double GetCurrentValue() const OVERRIDE;
 
+  // Change the current state of the animation to |new_value|.
+  void SetCurrentValue(double new_value);
+
   // Skip to the end of the current animation.
   void End();
 
   // Changes the length of the animation. This resets the current
   // state of the animation to the beginning.
   void SetDuration(int duration);
 
  protected:
   // Called when the animation progresses. Subclasses override this to
   // efficiently update their state.
-  virtual void AnimateToState(double state) = 0;
+  virtual void AnimateToState(double state) {}
 
   // Invoked by the AnimationContainer when the animation is running to advance
   // the animation. Use |time_now| rather than Time::Now to avoid multiple
   // animations running at the same time diverging.
   virtual void Step(base::TimeTicks time_now) OVERRIDE;
 
+  // Overriden to initialize state.
+  virtual void AnimationStarted() OVERRIDE;
+
   // Overriden to advance to the end (if End was invoked).
   virtual void AnimationStopped() OVERRIDE;
 
   // Overriden to return true if state is not 1.
   virtual bool ShouldSendCanceledFromStop() OVERRIDE;
 
  private:
   base::TimeDelta duration_;
 
   // Current state, on a scale from 0.0 to 1.0.
   double state_;
 
   // If true, we're in end. This is used to determine if the animation should
   // be advanced to the end from AnimationStopped.
   bool in_end_;
 
   DISALLOW_COPY_AND_ASSIGN(LinearAnimation);
 };
 
 }  // namespace ui
 
 #endif  // APP_LINEAR_ANIMATION_H_