Make MessageCenter a singleton object and build on Windows.

ash/system/web_notification/web_notification_tray.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/web_notification/web_notification_tray.h"
 
 #include "ash/shell.h"
 #include "ash/shell_window_ids.h"
 #include "ash/system/status_area_widget.h"
 #include "ash/system/tray/tray_bubble_wrapper.h"
@@ skipping 65 matching lines @@
   scoped_ptr<internal::TrayBubbleWrapper> bubble_wrapper_;
 };
 
 }  // namespace internal
 
 WebNotificationTray::WebNotificationTray(
     internal::StatusAreaWidget* status_area_widget)
     : internal::TrayBackgroundView(status_area_widget),
       button_(NULL),
       show_message_center_on_unlock_(false) {
-  message_center_.reset(new message_center::MessageCenter(this));
+  message_center_ = message_center::MessageCenter::GetInstance();
+  message_center_->AddObserver(this);
   button_ = new views::ImageButton(this);
   button_->set_triggerable_event_flags(
       ui::EF_LEFT_MOUSE_BUTTON | ui::EF_RIGHT_MOUSE_BUTTON);
   tray_container()->AddChildView(button_);
   UpdateTray();
 }
 
 WebNotificationTray::~WebNotificationTray() {
-  // message_center_ has a weak pointer to this; destroy it early.
-  message_center_.reset();
+  // Ensure the message center doesn't notify a destroyed object.
+  message_center_->RemoveObserver(this);
   // Release any child views that might have back pointers before ~View().
   message_center_bubble_.reset();
   popup_bubble_.reset();
   if (quiet_mode_bubble() && quiet_mode_bubble_->GetBubbleWidget())
     quiet_mode_bubble_->GetBubbleWidget()->RemoveObserver(this);
   quiet_mode_bubble_.reset();
 }
 
 void WebNotificationTray::ShowMessageCenterBubble() {
   if (status_area_widget()->login_status() == user::LOGGED_IN_LOCKED)
     return;
   if (quiet_mode_bubble())
     quiet_mode_bubble_.reset();
   if (message_center_bubble()) {
     UpdateTray();
     return;
   }
   // Indicate that the message center is visible. Clears the unread count.
   message_center_->SetMessageCenterVisible(true);
   UpdateTray();
   HidePopupBubble();
   message_center::MessageCenterBubble* bubble =
-      new message_center::MessageCenterBubble(message_center_.get());
+      new message_center::MessageCenterBubble(message_center_);
   message_center_bubble_.reset(
       new internal::WebNotificationBubbleWrapper(this, bubble));
 
   status_area_widget()->SetHideSystemNotifications(true);
   GetShelfLayoutManager()->UpdateAutoHideState();
 }
 
 void WebNotificationTray::HideMessageCenterBubble() {
   if (!message_center_bubble())
     return;
@@ skipping 19 matching lines @@
     return;
   if (!status_area_widget()->ShouldShowWebNotifications())
     return;
   UpdateTray();
   if (popup_bubble()) {
     popup_bubble()->bubble()->ScheduleUpdate();
   } else if (message_center_->HasPopupNotifications()) {
     popup_bubble_.reset(
         new internal::WebNotificationBubbleWrapper(
             this, new message_center::MessagePopupBubble(
-                message_center_.get())));
+                message_center_)));
   }
 }
 
 void WebNotificationTray::HidePopupBubble() {
   popup_bubble_.reset();
 }
 
 bool WebNotificationTray::ShouldShowQuietModeBubble(const ui::Event& event) {
   // TODO(mukai): Add keyboard event handler.
   if (!event.IsMouseEvent())
@@ skipping 117 matching lines @@
 gfx::Rect WebNotificationTray::GetAnchorRect(views::Widget* anchor_widget,
                                              AnchorType anchor_type,
                                              AnchorAlignment anchor_alignment) {
   return GetBubbleAnchorRect(anchor_widget, anchor_type, anchor_alignment);
 }
 
 void WebNotificationTray::HideBubble(const views::TrayBubbleView* bubble_view) {
   HideBubbleWithView(bubble_view);
 }
 
-void WebNotificationTray::MessageCenterChanged(bool new_notification) {
+void WebNotificationTray::OnMessageCenterChanged(bool new_notification) {
   if (message_center_bubble()) {
     if (message_center_->NotificationCount() == 0)
       HideMessageCenterBubble();
     else
       message_center_bubble()->bubble()->ScheduleUpdate();
   }
   if (popup_bubble()) {
     if (message_center_->NotificationCount() == 0)
       HidePopupBubble();
     else
@@ skipping 78 matching lines @@
 
 message_center::MessagePopupBubble*
 WebNotificationTray::GetPopupBubbleForTest() {
   if (!popup_bubble_.get())
     return NULL;
   return static_cast<message_center::MessagePopupBubble*>(
       popup_bubble_->bubble());
 }
 
 }  // namespace ash