Adds an ash global shortcut key for message center.

ash/system/web_notification/web_notification_tray.cc

 // 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.
 
 #include "ash/system/web_notification/web_notification_tray.h"
 
 #include "ash/root_window_controller.h"
 #include "ash/shell.h"
 #include "ash/shell_window_ids.h"
 #include "ash/system/status_area_widget.h"
@@ skipping 231 matching lines @@
           message_center_bubble()->bubble()->IsVisible());
 }
 
 bool WebNotificationTray::IsMouseInNotificationBubble() const {
   if (!popup_bubble())
     return false;
   return popup_bubble()->bubble_view()->GetBoundsInScreen().Contains(
       Shell::GetScreen()->GetCursorScreenPoint());
 }
 
+void WebNotificationTray::ShowMessageCenterBubble() {
+  if (!IsMessageCenterBubbleVisible())
+    message_center_tray_->ShowMessageCenterBubble();
+}
+
 void WebNotificationTray::SetShelfAlignment(ShelfAlignment alignment) {
   if (alignment == shelf_alignment())
     return;
   internal::TrayBackgroundView::SetShelfAlignment(alignment);
   // Destroy any existing bubble so that it will be rebuilt correctly.
   message_center_tray_->HideMessageCenterBubble();
   message_center_tray_->HidePopupBubble();
 }
 
 void WebNotificationTray::AnchorUpdated() {
@@ skipping 152 matching lines @@
 
 message_center::MessagePopupBubble*
 WebNotificationTray::GetPopupBubbleForTest() {
   if (!popup_bubble())
     return NULL;
   return static_cast<message_center::MessagePopupBubble*>(
       popup_bubble()->bubble());
 }
 
 }  // namespace ash