Refactor ViewsDelegate singleton

ui/views/views_delegate.cc

 // Copyright (c) 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 "ui/views/views_delegate.h"
 
 #include "base/command_line.h"
 #include "ui/views/views_touch_selection_controller_factory.h"
 
 #if defined(USE_AURA)
 #include "ui/views/touchui/touch_selection_menu_runner_views.h"
 #endif
 
 namespace views {
+namespace {
 
-ViewsDelegate::ViewsDelegate()
-    : views_tsc_factory_(new ViewsTouchEditingControllerFactory) {
-  ui::TouchEditingControllerFactory::SetInstance(views_tsc_factory_.get());
+ViewsDelegate* g_views_delegate = nullptr;
 
-#if defined(USE_AURA)
-  touch_selection_menu_runner_.reset(new TouchSelectionMenuRunnerViews());
-#endif
 }
 
 ViewsDelegate::~ViewsDelegate() {
-  ui::TouchEditingControllerFactory::SetInstance(NULL);
+  ui::TouchEditingControllerFactory::SetInstance(nullptr);
+
+  DCHECK_EQ(this, g_views_delegate);
+  g_views_delegate = nullptr;
+}
+
+ViewsDelegate* ViewsDelegate::GetInstance() {
+  return g_views_delegate;
 }
 
 void ViewsDelegate::SaveWindowPlacement(const Widget* widget,
                                         const std::string& window_name,
                                         const gfx::Rect& bounds,
                                         ui::WindowShowState show_state) {
 }
 
 bool ViewsDelegate::GetSavedWindowPlacement(
     const Widget* widget,
     const std::string& window_name,
     gfx::Rect* bounds,
     ui::WindowShowState* show_state) const {
   return false;
 }
 
 void ViewsDelegate::NotifyAccessibilityEvent(View* view,
                                              ui::AXEvent event_type) {
 }
 
 void ViewsDelegate::NotifyMenuItemFocused(const base::string16& menu_name,
                                           const base::string16& menu_item_name,
                                           int item_index,
                                           int item_count,
                                           bool has_submenu) {
 }
 
 #if defined(OS_WIN)
 HICON ViewsDelegate::GetDefaultWindowIcon() const {
-  return NULL;
+  return nullptr;
 }
 
 bool ViewsDelegate::IsWindowInMetro(gfx::NativeWindow window) const {
   return false;
 }
 #elif defined(OS_LINUX) && !defined(OS_CHROMEOS)
 gfx::ImageSkia* ViewsDelegate::GetDefaultWindowIcon() const {
-  return NULL;
+  return nullptr;
 }
 #endif
 
 NonClientFrameView* ViewsDelegate::CreateDefaultNonClientFrameView(
     Widget* widget) {
-  return NULL;
+  return nullptr;
 }
 
 void ViewsDelegate::AddRef() {
 }
 
 void ViewsDelegate::ReleaseRef() {
 }
 
 content::WebContents* ViewsDelegate::CreateWebContents(
     content::BrowserContext* browser_context,
     content::SiteInstance* site_instance) {
-  return NULL;
+  return nullptr;
 }
 
 base::TimeDelta ViewsDelegate::GetDefaultTextfieldObscuredRevealDuration() {
   return base::TimeDelta();
 }
 
 bool ViewsDelegate::WindowManagerProvidesTitleBar(bool maximized) {
   return false;
 }
 
 ui::ContextFactory* ViewsDelegate::GetContextFactory() {
-  return NULL;
+  return nullptr;
 }
 
 std::string ViewsDelegate::GetApplicationName() {
   base::FilePath program = base::CommandLine::ForCurrentProcess()->GetProgram();
   return program.BaseName().AsUTF8Unsafe();
 }
 
 #if defined(OS_WIN)
 int ViewsDelegate::GetAppbarAutohideEdges(HMONITOR monitor,
                                           const base::Closure& callback) {
   return EDGE_BOTTOM;
 }
 #endif
 
 scoped_refptr<base::TaskRunner> ViewsDelegate::GetBlockingPoolTaskRunner() {
   return nullptr;
 }
 
+ViewsDelegate::ViewsDelegate()
+    : views_tsc_factory_(new ViewsTouchEditingControllerFactory) {
+  DCHECK(!g_views_delegate);
+  g_views_delegate = this;
+
+  ui::TouchEditingControllerFactory::SetInstance(views_tsc_factory_.get());
+
+#if defined(USE_AURA)
+  touch_selection_menu_runner_.reset(new TouchSelectionMenuRunnerViews());
+#endif
+}
+
 }  // namespace views