Fix black background when locking with fullscreen window:

ui/compositor/layer_animation_observer.h

Index: ui/compositor/layer_animation_observer.h
diff --git a/ui/compositor/layer_animation_observer.h b/ui/compositor/layer_animation_observer.h
index 5a130708552fbd2610b4a3c3ff748ac9a0864195..63f146a7580c90617848dfb9e257098003a82264 100644
--- a/ui/compositor/layer_animation_observer.h
+++ b/ui/compositor/layer_animation_observer.h
@@ -8,6 +8,7 @@
 #include <set>
 
 #include "base/basictypes.h"
+#include "base/callback.h"
 #include "base/compiler_specific.h"
 #include "ui/compositor/compositor_export.h"
 
@@ -125,6 +126,108 @@ class COMPOSITOR_EXPORT ImplicitAnimationObserver
   bool first_sequence_scheduled_;
 };
 
+// This observer is intended to use in cases when some action have to be taken
+// once some animation successfully completes (i.e. it was not aborted).
+// Observer will count a number of sequences it is attached to, and a number of
+// finished sequences (either Ended or Aborted). Once these two numbers are
+// equal, observer will delete itself, calling callback passed to constructor if
+// there was no aborted animations.
+// This way it can be either used to wait for some animation to be finished in
+// multiple layers, to wait once a sequence of animations is finished in one
+// layer or the mixture of both.
+class COMPOSITOR_EXPORT AnimationFinishedObserver
+    : public LayerAnimationObserver {
+ public:
+  explicit AnimationFinishedObserver(base::Closure &callback);
+  virtual ~AnimationFinishedObserver();
+
+  // Pauses observer: no checks will be made while paused. It can be used when
+  // sequence have some immediate animations in the beginning.
+  void Pause();
+
+  // Unpauses observer. It does a check ant calls callback if conditions are
+  // met.
+  void Unpause();
+
+ private:
+  // LayerAnimationObserver implementation
+  virtual void OnLayerAnimationEnded(
+      LayerAnimationSequence* sequence) OVERRIDE;
+  virtual void OnLayerAnimationAborted(
+      LayerAnimationSequence* sequence) OVERRIDE;
+  virtual void OnLayerAnimationScheduled(
+      LayerAnimationSequence* sequence) OVERRIDE {};
+  virtual void OnAttachedToSequence(
+      LayerAnimationSequence* sequence) OVERRIDE;
+
+  // Callback to be called.
+  base::Closure callback_;
+
+  // Number of sequences this observer was attached to.
+  int sequences_attached_;
+
+  // Number of sequences either ended or aborted.
+  int sequences_completed_;
+
+  bool paused_;
+
+  DISALLOW_COPY_AND_ASSIGN(AnimationFinishedObserver);
+};
+
+// This observer is intended to use in cases when some action have to be taken
+// once some animation was aborted. Observer will count a number of sequences it
+// is attached to, and a number of finished sequences (either Ended or Aborted).
+// Once these two numbers are equal, observer will delete itself, calling
+// callback passed to constructor if there was at least one aborted animation.
+// This way it can be either used to wait for some animation to be cancelled in
+// multiple layers, to wait once a sequence of animations is cancelled in one
+// layer or the mixture of both.
+// If this observer is deleted before all animations complete, it will call
+// |callback|, so it is safe to use it in conjunction with
+// AnimationFinishedObserver to clean up resources.
+
+class COMPOSITOR_EXPORT AnimationAbortedObserver
+    : public LayerAnimationObserver {
+ public:
+  explicit AnimationAbortedObserver(base::Closure &callback);
+  virtual ~AnimationAbortedObserver();
+
+  // Pauses observer: no checks will be made while paused. It can be used when
+  // sequence have some immediate animations in the beginning.
+  void Pause();
+
+  // Unpauses observer. It does a check ant calls callback if conditions are
+  // met.
+  void Unpause();
+
+ private:
+  // LayerAnimationObserver implementation
+  virtual void OnLayerAnimationEnded(
+      LayerAnimationSequence* sequence) OVERRIDE;
+  virtual void OnLayerAnimationAborted(
+      LayerAnimationSequence* sequence) OVERRIDE;
+  virtual void OnLayerAnimationScheduled(
+      LayerAnimationSequence* sequence) OVERRIDE {};
+  virtual void OnAttachedToSequence(
+      LayerAnimationSequence* sequence) OVERRIDE;
+
+  // Callback to be called.
+  base::Closure callback_;
+
+  // Number of sequences this observer was attached to.
+  int sequences_attached_;
+
+  // Number of sequences either ended or aborted.
+  int sequences_completed_;
+
+  // True if at lease one sequence was aborted.
+  bool aborted_;
+
+  bool paused_;
+
+  DISALLOW_COPY_AND_ASSIGN(AnimationAbortedObserver);
+};
+
 }  // namespace ui
 
 #endif  // UI_COMPOSITOR_LAYER_ANIMATION_OBSERVER_H_