Fix black background when locking with fullscreen window:

ui/base/animation/animation_container.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_ANIMATION_CONTAINER_H_
 #define UI_BASE_ANIMATION_ANIMATION_CONTAINER_H_
 
 #include <set>
 
 #include "base/memory/ref_counted.h"
 #include "base/time.h"
 #include "base/timer.h"
 #include "ui/base/ui_export.h"
 
 namespace ui {
 
 class AnimationContainerElement;
 class AnimationContainerObserver;
 
+namespace test {
+class AnimationContainerTestHelper;
+}
+
 // AnimationContainer is used by Animation to manage the underlying timer.
 // Internally each Animation creates a single AnimationContainer. You can
 // group a set of Animations into the same AnimationContainer by way of
 // Animation::SetContainer. Grouping a set of Animations into the same
 // AnimationContainer ensures they all update and start at the same time.
 //
 // AnimationContainer is ref counted. Each Animation contained within the
 // AnimationContainer own it.
 class UI_EXPORT AnimationContainer
     : public base::RefCounted<AnimationContainer> {
@@ skipping 16 matching lines @@
   }
 
   // The time the last animation ran at.
   base::TimeTicks last_tick_time() const { return last_tick_time_; }
 
   // Are there any timers running?
   bool is_running() const { return !elements_.empty(); }
 
  private:
   friend class base::RefCounted<AnimationContainer>;
+  friend class test::AnimationContainerTestHelper;
 
   typedef std::set<AnimationContainerElement*> Elements;
 
   ~AnimationContainer();
 
   // Timer callback method.
   void Run();
 
   // Sets min_timer_interval_ and restarts the timer.
   void SetMinTimerInterval(base::TimeDelta delta);
@@ skipping 16 matching lines @@
   base::RepeatingTimer<AnimationContainer> timer_;
 
   AnimationContainerObserver* observer_;
 
   DISALLOW_COPY_AND_ASSIGN(AnimationContainer);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_ANIMATION_ANIMATION_CONTAINER_H_