content: convert user action notification to observer usage

chrome/browser/ui/webui/user_actions/user_actions_ui_handler.h

 // Copyright 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.
 
 #ifndef CHROME_BROWSER_UI_WEBUI_USER_ACTIONS_USER_ACTIONS_UI_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_USER_ACTIONS_USER_ACTIONS_UI_HANDLER_H_
 
-#include "content/public/browser/notification_observer.h"
-#include "content/public/browser/notification_registrar.h"
+#include "content/public/browser/user_metrics.h"
 #include "content/public/browser/web_ui_message_handler.h"
 
 // UI Handler for chrome://user-actions/
 // It listens to user action notifications and passes those notifications
 // into the Javascript to update the page.
-class UserActionsUIHandler : public content::NotificationObserver,
-                             public content::WebUIMessageHandler {
+class UserActionsUIHandler : public content::WebUIMessageHandler {
  public:
   UserActionsUIHandler();
   virtual ~UserActionsUIHandler();
 
-  // NotificationObserver implementation:
-  // Listens for user action notifications and passes the message to
-  // observeUserAction in user_actions.js.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
-
   // WebUIMessageHandler implementation:
   // Does nothing for now.
   virtual void RegisterMessages() OVERRIDE;
 
  private:
-  content::NotificationRegistrar registrar_;
+  void OnUserAction(const std::string& action);
+
+  content::ActionCallback action_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(UserActionsUIHandler);
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_USER_ACTIONS_USER_ACTIONS_UI_HANDLER_H_