cros: Fix unlock crash with multi-display

ash/wm/session_state_animator.h

 // Copyright (c) 2012 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 ASH_WM_SESSION_STATE_ANIMATOR_H_
 #define ASH_WM_SESSION_STATE_ANIMATOR_H_
 
 #include "ash/ash_export.h"
 #include "base/callback.h"
 #include "base/macros.h"
@@ skipping 174 matching lines @@
   // Reports animation duration for |speed|.
   virtual base::TimeDelta GetDuration(AnimationSpeed speed);
 
   // Apply animation |type| to all containers included in |container_mask| with
   // specified |speed|.
   virtual void StartAnimation(int container_mask,
                               AnimationType type,
                               AnimationSpeed speed) = 0;
 
   // Apply animation |type| to all containers included in |container_mask| with
-  // specified |speed| and call a |callback| at the end of the animation, if it
-  // is not null.
+  // specified |speed| and call a |callback| once at the end of the animations,
+  // if it is not null.
   virtual void StartAnimationWithCallback(int container_mask,
                                           AnimationType type,
                                           AnimationSpeed speed,
                                           base::Closure callback) = 0;
 
   // Begins an animation sequence.  Use this when you need to be notified when
   // a group of animations are completed.  See AnimationSequence documentation
   // for more details.
   virtual AnimationSequence* BeginAnimationSequence(base::Closure callback) = 0;
 
   // Retruns true if the wallpaper is hidden.
   virtual bool IsWallpaperHidden() const = 0;
 
   // Shows the wallpaper immediately.
   virtual void ShowWallpaper() = 0;
 
   // Hides the wallpaper immediately.
   virtual void HideWallpaper() = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(SessionStateAnimator);
 };
 
 }  // namespace ash
 
 #endif  // ASH_WM_SESSION_STATE_ANIMATOR_H_