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

ash/system/chromeos/rotation/tray_rotation_lock.cc

 // Copyright 2014 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/chromeos/rotation/tray_rotation_lock.h"
 
 #include "ash/display/screen_orientation_controller_chromeos.h"
 #include "ash/shell.h"
 #include "ash/system/tray/system_tray.h"
 #include "ash/system/tray/tray_item_more.h"
@@ skipping 132 matching lines @@
              ->maximize_mode_controller()
              ->IsMaximizeModeWindowManagerEnabled() &&
          Shell::GetInstance()
              ->screen_orientation_controller()
              ->rotation_locked();
 }
 
 bool TrayRotationLock::OnPrimaryDisplay() const {
   gfx::NativeView native_view = system_tray()->GetWidget()->GetNativeView();
   gfx::Display parent_display =
-      Shell::GetScreen()->GetDisplayNearestWindow(native_view);
+      gfx::Screen::GetScreen()->GetDisplayNearestWindow(native_view);
   return parent_display.IsInternal();
 }
 
 void TrayRotationLock::StopObservingRotation() {
   if (!observing_rotation_)
     return;
   ScreenOrientationController* controller =
       Shell::GetInstance()->screen_orientation_controller();
   if (controller)
     controller->RemoveObserver(this);
   observing_rotation_ = false;
 }
 
 void TrayRotationLock::StopObservingShell() {
   if (!observing_shell_)
     return;
   Shell::GetInstance()->RemoveShellObserver(this);
   observing_shell_ = false;
 }
 
 }  // namespace ash