Refactor ViewsDelegate singleton

ui/message_center/views/message_popup_collection.cc

 // 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.
 
 #include "ui/message_center/views/message_popup_collection.h"
 
 #include <set>
 
 #include "base/bind.h"
 #include "base/i18n/rtl.h"
@@ skipping 153 matching lines @@
 
     toast->RevealWithAnimation(origin);
 
     // Shift the base line to be a few pixels above the last added toast or (few
     // pixels below last added toast if top-aligned).
     if (top_down)
       base += view_height + kToastMarginY;
     else
       base -= view_height + kToastMarginY;
 
-    if (views::ViewsDelegate::views_delegate) {
-      views::ViewsDelegate::views_delegate->NotifyAccessibilityEvent(
+    if (views::ViewsDelegate::GetInstance()) {
+      views::ViewsDelegate::GetInstance()->NotifyAccessibilityEvent(
           toast, ui::AX_EVENT_ALERT);
     }
 
     message_center_->DisplayedNotification(
         (*iter)->id(), message_center::DISPLAY_SOURCE_POPUP);
   }
 }
 
 void MessagePopupCollection::OnMouseEntered(ToastContentsView* toast_entered) {
   // Sometimes we can get two MouseEntered/MouseExited in a row when animating
@@ skipping 314 matching lines @@
       views::Widget* widget = (*iter)->GetWidget();
       if (widget)
         return widget->GetWindowBoundsInScreen();
       break;
     }
   }
   return gfx::Rect();
 }
 
 }  // namespace message_center