Refactor ViewsDelegate singleton

ash/shell/content_client/shell_browser_main_parts.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/shell/content_client/shell_browser_main_parts.h"
 
 #include "ash/ash_switches.h"
 #include "ash/desktop_background/desktop_background_controller.h"
 #include "ash/shell.h"
 #include "ash/shell/shell_delegate_impl.h"
@@ skipping 90 matching lines @@
 void ShellBrowserMainParts::ToolkitInitialized() {
   wm_state_.reset(new wm::WMState);
 }
 
 void ShellBrowserMainParts::PreMainMessageLoopRun() {
   net_log_.reset(new content::ShellNetLog("ash_shell"));
   browser_context_.reset(new content::ShellBrowserContext(
       false, net_log_.get()));
 
   // A ViewsDelegate is required.
-  if (!views::ViewsDelegate::views_delegate)
-    views::ViewsDelegate::views_delegate = new ShellViewsDelegate;
+  if (!views::ViewsDelegate::GetInstance())
+    views_delegate_.reset(new ShellViewsDelegate);
 
   delegate_ = new ash::shell::ShellDelegateImpl;
   // The global message center state must be initialized absent
   // g_browser_process.
   message_center::MessageCenter::Initialize();
 
 #if defined(OS_CHROMEOS)
   // Create CrasAudioHandler for testing since g_browser_process
   // is absent.
   chromeos::CrasAudioHandler::InitializeForTesting();
@@ skipping 43 matching lines @@
   browser_context_.reset();
 }
 
 bool ShellBrowserMainParts::MainMessageLoopRun(int* result_code) {
   base::MessageLoopForUI::current()->Run();
   return true;
 }
 
 }  // namespace shell
 }  // namespace ash