Refactor ViewsDelegate singleton

ui/views/test/test_views_delegate_aura.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 "ui/views/test/test_views_delegate.h"
 
 #include "ui/aura/env.h"
 #include "ui/wm/core/wm_state.h"
 
 #if !defined(OS_CHROMEOS)
 #include "ui/views/widget/desktop_aura/desktop_native_widget_aura.h"
 #endif  // !defined(OS_CHROMEOS)
 
 
 namespace views {
 
 TestViewsDelegate::TestViewsDelegate()
     : context_factory_(nullptr),
       use_desktop_native_widgets_(false),
       use_transparent_windows_(false) {
-  DCHECK(!ViewsDelegate::views_delegate);
-  ViewsDelegate::views_delegate = this;
 #if defined(USE_AURA)
   wm_state_.reset(new wm::WMState);
 #endif
 }
 
 TestViewsDelegate::~TestViewsDelegate() {
-  if (ViewsDelegate::views_delegate == this)
-    ViewsDelegate::views_delegate = NULL;
 }
 
 #if defined(OS_WIN)
 HICON TestViewsDelegate::GetSmallWindowIcon() const {
   return nullptr;
 }
 #endif
 
 void TestViewsDelegate::OnBeforeWidgetInit(
     Widget::InitParams* params,
@@ skipping 11 matching lines @@
 
 ui::ContextFactory* TestViewsDelegate::GetContextFactory() {
   if (context_factory_)
     return context_factory_;
   if (aura::Env::GetInstance())
     return aura::Env::GetInstance()->context_factory();
   return nullptr;
 }
 
 }  // namespace views