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

ash/system/chromeos/tray_display.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/chromeos/tray_display.h"
 
 #include <utility>
 #include <vector>
 
 #include "ash/display/display_manager.h"
@@ skipping 232 matching lines @@
             IDS_ASH_STATUS_TRAY_DISPLAY_MIRRORING,
             GetDisplayName(display_manager->mirroring_display_id()));
       }
       return l10n_util::GetStringUTF16(
           IDS_ASH_STATUS_TRAY_DISPLAY_MIRRORING_NO_INTERNAL);
     }
 
     if (display_manager->IsInUnifiedMode())
       return l10n_util::GetStringUTF16(IDS_ASH_STATUS_TRAY_DISPLAY_UNIFIED);
 
-    int64_t primary_id = Shell::GetScreen()->GetPrimaryDisplay().id();
+    int64_t primary_id = gfx::Screen::GetScreen()->GetPrimaryDisplay().id();
     if (gfx::Display::HasInternalDisplay() &&
         !(gfx::Display::IsInternalDisplayId(primary_id))) {
       if (additional_message_out) {
         *additional_message_out = ash::SubstituteChromeOSDeviceType(
             IDS_ASH_STATUS_TRAY_DISPLAY_DOCKED_DESCRIPTION);
       }
       return l10n_util::GetStringUTF16(IDS_ASH_STATUS_TRAY_DISPLAY_DOCKED);
     }
 
     return base::string16();
@@ skipping 180 matching lines @@
 bool TrayDisplay::GetAccessibleStateForTesting(ui::AXViewState* state) {
   views::View* view = default_;
   if (view) {
     view->GetAccessibleState(state);
     return true;
   }
   return false;
 }
 
 }  // namespace ash