Fix black background when locking with fullscreen window:

ui/compositor/layer_animator.h

Index: ui/compositor/layer_animator.h
diff --git a/ui/compositor/layer_animator.h b/ui/compositor/layer_animator.h
index 6c24008cb0d7698e1cb2ecca9d43bd3de14a8244..1945a8ab0c3db05f9d48125b3afd98648ea871b0 100644
--- a/ui/compositor/layer_animator.h
+++ b/ui/compositor/layer_animator.h
@@ -14,6 +14,7 @@
 #include "base/observer_list.h"
 #include "base/time.h"
 #include "ui/base/animation/animation_container_element.h"
+#include "ui/base/animation/animation_container_test_helper.h"
 #include "ui/base/animation/tween.h"
 #include "ui/compositor/compositor_export.h"
 #include "ui/compositor/layer_animation_element.h"
@@ -193,6 +194,12 @@ class COMPOSITOR_EXPORT LayerAnimator
     return disable_animations_for_test_;
   }
 
+  // Creates AnimationContainerTestHelper that would give fine control over
+  // animation progress. Other test flags (disable_animations_for_test /
+  // disable_timer_for_test) should be turned off.
+  static scoped_ptr<test::AnimationContainerTestHelper>
+    CreateAnimatorHelperForTest();
+
  protected:
   virtual ~LayerAnimator();