Add the "virtual" keyword on method overrides that are missing it.

app/slide_animation.h

 // Copyright (c) 2010 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 APP_SLIDE_ANIMATION_H_
 #define APP_SLIDE_ANIMATION_H_
 #pragma once
 
 #include "app/linear_animation.h"
 #include "app/tween.h"
@@ skipping 47 matching lines @@
   // Begin a hiding animation or reverse a showing animation in progress.
   virtual void Hide();
 
   // Sets the time a slide will take. Note that this isn't actually
   // the amount of time an animation will take as the current value of
   // the slide is considered.
   virtual void SetSlideDuration(int duration) { slide_duration_ = duration; }
   int GetSlideDuration() const { return slide_duration_; }
   void SetTweenType(Tween::Type tween_type) { tween_type_ = tween_type; }
 
-  double GetCurrentValue() const { return value_current_; }
+  virtual double GetCurrentValue() const { return value_current_; }
   bool IsShowing() const { return showing_; }
   bool IsClosing() const { return !showing_ && value_end_ < value_current_; }
 
  private:
   // Overridden from Animation.
-  void AnimateToState(double state);
+  virtual void AnimateToState(double state);
 
   AnimationDelegate* target_;
 
   Tween::Type tween_type_;
 
   // Used to determine which way the animation is going.
   bool showing_;
 
   // Animation values. These are a layer on top of Animation::state_ to
   // provide the reversability.
   double value_start_;
   double value_end_;
   double value_current_;
 
   // How long a hover in/out animation will last for. This defaults to
   // kHoverFadeDurationMS, but can be overridden with SetDuration.
   int slide_duration_;
 
   DISALLOW_COPY_AND_ASSIGN(SlideAnimation);
 };
 
 #endif  // APP_SLIDE_ANIMATION_H_