Remove now-unnecessary wrappers around gfx::Screen::GetScreen()

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/ash_switches.h"
 #include "ash/root_window_controller.h"
 #include "ash/shelf/shelf_layout_manager.h"
 #include "ash/shelf/shelf_layout_manager_observer.h"
@@ skipping 171 matching lines @@
       this,
       message_center::MessageCenter::Get()));
   popup_alignment_delegate_.reset(new AshPopupAlignmentDelegate());
   popup_collection_.reset(new message_center::MessagePopupCollection(
       ash::Shell::GetContainer(
           status_area_widget->GetNativeView()->GetRootWindow(),
           kShellWindowId_StatusContainer),
       message_center(),
       message_center_tray_.get(),
       popup_alignment_delegate_.get()));
-  const gfx::Display& display = Shell::GetScreen()->GetDisplayNearestWindow(
-      status_area_widget->GetNativeView());
-  popup_alignment_delegate_->StartObserving(Shell::GetScreen(), display);
+  const gfx::Display& display =
+      gfx::Screen::GetScreen()->GetDisplayNearestWindow(
+          status_area_widget->GetNativeView());
+  popup_alignment_delegate_->StartObserving(gfx::Screen::GetScreen(), display);
   OnMessageCenterTrayChanged();
 }
 
 WebNotificationTray::~WebNotificationTray() {
   // Release any child views that might have back pointers before ~View().
   message_center_bubble_.reset();
   popup_alignment_delegate_.reset();
   popup_collection_.reset();
 }
 
@@ skipping 288 matching lines @@
 
 message_center::MessageCenterBubble*
 WebNotificationTray::GetMessageCenterBubbleForTest() {
   if (!message_center_bubble())
     return NULL;
   return static_cast<message_center::MessageCenterBubble*>(
       message_center_bubble()->bubble());
 }
 
 }  // namespace ash