Fix the bug of multiple overlays.

ash/wm/overlay_event_filter.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_OVERLAY_EVENT_FILTER_H_
 #define ASH_WM_OVERLAY_EVENT_FILTER_H_
 
 #include "ash/ash_export.h"
 #include "ash/shell_observer.h"
 #include "base/compiler_specific.h"
@@ skipping 28 matching lines @@
   OverlayEventFilter();
   virtual ~OverlayEventFilter();
 
   // Starts the filtering of events.  It also notifies the specified
   // |delegate| when a key event means cancel (like Esc).  It holds the
   // pointer to the specified |delegate| until Deactivate() is called, but
   // does not take ownership.
   void Activate(Delegate* delegate);
 
   // Ends the filtering of events.
-  void Deactivate();
+  void Deactivate(Delegate* delegate);
 
   // Cancels the partial screenshot UI.  Do nothing if it's not activated.
   void Cancel();
 
+  // Returns true if it's currently active.
+  bool IsActive();
+
   // ui::EventHandler overrides:
   virtual void OnKeyEvent(ui::KeyEvent* event) OVERRIDE;
 
   // ShellObserver overrides:
   virtual void OnLoginStateChanged(user::LoginStatus status) OVERRIDE;
   virtual void OnAppTerminating() OVERRIDE;
   virtual void OnLockStateChanged(bool locked) OVERRIDE;
 
  private:
+  FRIEND_TEST_ALL_PREFIXES(PartialScreenshotViewTest, DontStartOverOverlay);
+
   Delegate* delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(OverlayEventFilter);
 };
 
 }  // namespace ash
 
 #endif  // ASH_WM_OVERLAY_EVENT_FILTER_H_