Add context to gfx::Screen calls in support of simultaneous desktop+ash

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/shell.h"
 #include "ash/system/status_area_widget.h"
 #include "ash/system/tray/tray_bubble_view.h"
 #include "ash/system/tray/tray_constants.h"
@@ skipping 183 matching lines @@
 }
 
 bool WebNotificationTray::IsMessageCenterBubbleVisible() const {
   return (message_center_bubble() && message_center_bubble_->IsVisible());
 }
 
 bool WebNotificationTray::IsMouseInNotificationBubble() const {
   if (!popup_bubble())
     return false;
   return popup_bubble_->bubble_view()->GetBoundsInScreen().Contains(
-      gfx::Screen::GetCursorScreenPoint());
+      Shell::GetAshScreen()->GetCursorScreenPoint());
 }
 
 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.
   HideMessageCenterBubble();
   HidePopupBubble();
 }
@@ skipping 162 matching lines @@
   return message_center_bubble()->NumMessageViewsForTest();
 }
 
 size_t WebNotificationTray::GetPopupNotificationCountForTest() const {
   if (!popup_bubble())
     return 0;
   return popup_bubble()->NumMessageViewsForTest();
 }
 
 }  // namespace ash