Realign message center popups when displays are added or removed

ui/message_center/views/desktop_popup_alignment_delegate.h

 // Copyright 2014 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_VIEWS_DESKTOP_POPUP_ALIGNMENT_DELEGATE_H_
 #define UI_MESSAGE_CENTER_VIEWS_DESKTOP_POPUP_ALIGNMENT_DELEGATE_H_
 
 #include <stdint.h>
 
 #include "base/macros.h"
@@ skipping 31 matching lines @@
  private:
   friend class test::MessagePopupCollectionTest;
 
   enum PopupAlignment {
     POPUP_ALIGNMENT_TOP = 1 << 0,
     POPUP_ALIGNMENT_LEFT = 1 << 1,
     POPUP_ALIGNMENT_BOTTOM = 1 << 2,
     POPUP_ALIGNMENT_RIGHT = 1 << 3,
   };
 
+  void UpdatePrimaryDisplay();
+
   // Overridden from display::DisplayObserver:
   void OnDisplayAdded(const display::Display& new_display) override;
   void OnDisplayRemoved(const display::Display& old_display) override;
   void OnDisplayMetricsChanged(const display::Display& display,
                                uint32_t metrics) override;
 
   int32_t alignment_;
-  int64_t display_id_;
+  int64_t primary_display_id_;
   display::Screen* screen_;
   gfx::Rect work_area_;
 
   DISALLOW_COPY_AND_ASSIGN(DesktopPopupAlignmentDelegate);
 };
 
 }  // namespace message_center
 
 #endif  // UI_MESSAGE_CENTER_VIEWS_DESKTOP_POPUP_ALIGNMENT_DELEGATE_H_