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

ash/system/tray/system_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/tray/system_tray.h"
 
 #include "ash/ash_switches.h"
 #include "ash/metrics/user_metrics_recorder.h"
 #include "ash/shelf/shelf_layout_manager.h"
 #include "ash/shell.h"
@@ skipping 347 matching lines @@
   return ((system_bubble_.get() &&
            system_bubble_->bubble()->IsVisible()) ||
           (notification_bubble_.get() &&
            notification_bubble_->bubble()->IsVisible()));
 }
 
 bool SystemTray::IsMouseInNotificationBubble() const {
   if (!notification_bubble_)
     return false;
   return notification_bubble_->bubble_view()->GetBoundsInScreen().Contains(
-      Shell::GetScreen()->GetCursorScreenPoint());
+      gfx::Screen::GetScreen()->GetCursorScreenPoint());
 }
 
 bool SystemTray::CloseSystemBubble() const {
   if (!system_bubble_)
     return false;
   system_bubble_->bubble()->Close();
   return true;
 }
 
 views::View* SystemTray::GetHelpButtonView() const {
@@ skipping 209 matching lines @@
 
 void SystemTray::UpdateWebNotifications() {
   TrayBubbleView* bubble_view = NULL;
   if (notification_bubble_)
     bubble_view = notification_bubble_->bubble_view();
   else if (system_bubble_)
     bubble_view = system_bubble_->bubble_view();
 
   int height = 0;
   if (bubble_view) {
-    gfx::Rect work_area = Shell::GetScreen()->GetDisplayNearestWindow(
-        bubble_view->GetWidget()->GetNativeView()).work_area();
+    gfx::Rect work_area =
+        gfx::Screen::GetScreen()
+            ->GetDisplayNearestWindow(bubble_view->GetWidget()->GetNativeView())
+            .work_area();
     if (GetShelfLayoutManager()->GetAlignment() != SHELF_ALIGNMENT_TOP) {
       height = std::max(
           0, work_area.height() - bubble_view->GetBoundsInScreen().y());
     } else {
       height = std::max(
           0, bubble_view->GetBoundsInScreen().bottom() - work_area.y());
     }
   }
   status_area_widget()->web_notification_tray()->SetSystemTrayHeight(height);
 }
@@ skipping 123 matching lines @@
   system_bubble_.reset();
   // When closing a system bubble with the alternate shelf layout, we need to
   // turn off the active tinting of the shelf.
   if (full_system_tray_menu_) {
     SetDrawBackgroundAsActive(false);
     full_system_tray_menu_ = false;
   }
 }
 
 }  // namespace ash