Add UMA histogram data representing the Synced Notifications feature.

chrome/browser/notifications/message_center_stats_collector.cc

 // Copyright 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 "chrome/browser/notifications/message_center_stats_collector.h"
 
 #include <string>
 
 #include "base/metrics/histogram.h"
 #include "content/public/browser/user_metrics.h"
@@ skipping 116 matching lines @@
           content::UserMetricsAction("Notifications.ShowMessageCenter"));
       break;
     case message_center::VISIBILITY_SETTINGS:
       content::RecordAction(
           content::UserMetricsAction("Notifications.ShowSettings"));
       break;
   }
 }
 
 void MessageCenterStatsCollector::OnQuietModeChanged(bool in_quiet_mode) {
+  if (in_quiet_mode) {
+    content::RecordAction(
+        content::UserMetricsAction("Notifications.Mute"));
+  } else {
+    content::RecordAction(
+        content::UserMetricsAction("Notifications.Unmute"));
+  }
 }