Make MessageCenter a singleton object and build on Windows.

chrome/browser/notifications/message_center_notification_manager.h

Index: chrome/browser/notifications/message_center_notification_manager.h
diff --git a/chrome/browser/notifications/message_center_notification_manager.h b/chrome/browser/notifications/message_center_notification_manager.h
index d4b2651e2b7bdf3e6c2d72e2469fecb9ddc6790a..497c2646592be43d997bab68262d2b91265bc22e 100644
--- a/chrome/browser/notifications/message_center_notification_manager.h
+++ b/chrome/browser/notifications/message_center_notification_manager.h
@@ -14,6 +14,10 @@
 class Notification;
 class Profile;
 
+namespace message_center {
+class MessageCenter;
+}
+
 // This class extends NotificationUIManagerImpl and delegates actual display
 // of notifications to MessageCenter, doing necessary conversions.
 class MessageCenterNotificationManager : public NotificationUIManagerImpl {
@@ -33,6 +37,8 @@ class MessageCenterNotificationManager : public NotificationUIManagerImpl {
   virtual bool UpdateNotification(const Notification& notification) OVERRIDE;
 
  private:
+  message_center::MessageCenter* message_center_;
+
   DISALLOW_COPY_AND_ASSIGN(MessageCenterNotificationManager);
 };