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

chrome/browser/ui/ash/launcher/browser_status_monitor.cc

 // Copyright 2013 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 "chrome/browser/ui/ash/launcher/browser_status_monitor.h"
 
 #include "ash/display/window_tree_host_manager.h"
 #include "ash/shelf/shelf_util.h"
 #include "ash/shell.h"
 #include "ash/wm/window_util.h"
@@ skipping 110 matching lines @@
     aura::Window::Windows root_windows = ash::Shell::GetAllRootWindows();
     aura::Window::Windows::const_iterator iter = root_windows.begin();
     for (; iter != root_windows.end(); ++iter) {
       // |observed_activation_clients_| can have the same activation client
       // multiple times - which would be handled by the used
       // |ScopedObserverWithDuplicatedSources|.
       observed_activation_clients_.Add(
           aura::client::GetActivationClient(*iter));
       observed_root_windows_.Add(static_cast<aura::Window*>(*iter));
     }
-    ash::Shell::GetInstance()->GetScreen()->AddObserver(this);
+    gfx::Screen::GetScreen()->AddObserver(this);
   }
 
   browser_tab_strip_tracker_.Init(
       BrowserTabStripTracker::InitWith::ALL_BROWERS);
 }
 
 BrowserStatusMonitor::~BrowserStatusMonitor() {
   // This check needs for win7_aura. Without this, all tests in
   // ChromeLauncherController will fail in win7_aura.
   if (ash::Shell::HasInstance())
-    ash::Shell::GetInstance()->GetScreen()->RemoveObserver(this);
+    gfx::Screen::GetScreen()->RemoveObserver(this);
 
   chrome::SettingsWindowManager::GetInstance()->RemoveObserver(
       settings_window_observer_.get());
 
   browser_tab_strip_tracker_.StopObservingAndSendOnBrowserRemoved();
 
   STLDeleteContainerPairSecondPointers(webcontents_to_observer_map_.begin(),
                                        webcontents_to_observer_map_.end());
 }
 
@@ skipping 231 matching lines @@
     content::WebContents* contents) {
   return launcher_controller_->GetShelfIDForWebContents(contents);
 }
 
 void BrowserStatusMonitor::SetShelfIDForBrowserWindowContents(
     Browser* browser,
     content::WebContents* web_contents) {
   launcher_controller_->GetBrowserShortcutLauncherItemController()->
       SetShelfIDForBrowserWindowContents(browser, web_contents);
 }