Add UMA histogram data representing the Synced Notifications feature.

chrome/browser/notifications/sync_notifier/chrome_notifier_delegate.h

 // 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.
 
 #ifndef CHROME_BROWSER_NOTIFICATIONS_SYNC_NOTIFIER_CHROME_NOTIFIER_DELEGATE_H_
 #define CHROME_BROWSER_NOTIFICATIONS_SYNC_NOTIFIER_CHROME_NOTIFIER_DELEGATE_H_
 
+#include <map>
 #include <string>
 
 #include "chrome/browser/notifications/notification_delegate.h"
+#include "chrome/browser/notifications/sync_notifier/synced_notification_stats.h"
 #include "url/gurl.h"
 
 namespace notifier {
 
 class ChromeNotifierService;
 
 // ChromeNotifierDelegate is a NotificationDelegate which catches
 // responses from the NotificationUIManager when a notification
 // has been closed.
 
@@ skipping 14 matching lines @@
 
   virtual content::RenderViewHost* GetRenderViewHost() const OVERRIDE;
 
  private:
   virtual ~ChromeNotifierDelegate();
   void NavigateToUrl(const GURL& destination) const;
 
   const std::string notification_id_;
   ChromeNotifierService* const chrome_notifier_;
 
+  typedef std::map<std::string, SyncedNotificationStats> StatsCollection;
+  StatsCollection stats_;
+
   DISALLOW_COPY_AND_ASSIGN(ChromeNotifierDelegate);
 };
 
 }  // namespace notifier
 
 #endif  // CHROME_BROWSER_NOTIFICATIONS_SYNC_NOTIFIER_CHROME_NOTIFIER_DELEGATE_H_