Hide notifications popups when entering fullscreen mode.

ui/message_center/message_center_tray_delegate.h

 // Copyright (c) 2013 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_MESSAGE_CENTER_MESSAGE_CENTER_TRAY_DELEGATE_H_
 #define UI_MESSAGE_CENTER_MESSAGE_CENTER_TRAY_DELEGATE_H_
 
 #include "ui/message_center/message_center_export.h"
 
 namespace message_center {
 
+class MessageCenterTray;
+
 // A MessageCenterTrayDelegate class is responsible for managing the various UI
 // surfaces that should be displayed when the MessageCenter is changed.
 class MESSAGE_CENTER_EXPORT MessageCenterTrayDelegate {
  public:
   virtual ~MessageCenterTrayDelegate() {};
 
   // Called whenever a change to the visible UI has occurred.
   virtual void OnMessageCenterTrayChanged() = 0;
 
   // Display the popup bubbles for new notifications to the user.  Returns true
   // if popups were actually displayed to the user.
   virtual bool ShowPopups() = 0;
 
   // Remove the popup bubbles from the UI.
   virtual void HidePopups() = 0;
 
   // Display the message center containing all undismissed notifications to the
   // user.  Returns true if the center was actually displayed to the user.
   virtual bool ShowMessageCenter() = 0;
 
   // Remove the message center from the UI.
   virtual void HideMessageCenter() = 0;
 
   // Display the notifier settings as a bubble.
   virtual bool ShowNotifierSettings() = 0;
 
   // Show a platform-specific UI that informs the user how to open the message
   // center.
-  virtual void DisplayFirstRunBalloon() {};
+  virtual void DisplayFirstRunBalloon() {}
+
+  virtual MessageCenterTray* GetMessageCenterTray() = 0;
 };
 
 }  // namespace message_center
 
 #endif  // UI_MESSAGE_CENTER_MESSAGE_CENTER_TRAY_DELEGATE_H_