[Sync] Make P2PNotifier emit a notification only if some enabled types changed

sync/notifier/p2p_notifier.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 "sync/notifier/p2p_notifier.h"
 
 #include <algorithm>
 
 #include "base/json/json_reader.h"
 #include "base/json/json_writer.h"
@@ skipping 242 matching lines @@
     LOG(WARNING) << "Could not parse notification data from "
                  << notification.data;
     notification_data =
         P2PNotificationData(unique_id_, NOTIFY_ALL, enabled_types_);
   }
   if (!notification_data.IsTargeted(unique_id_)) {
     DVLOG(1) << "Not a target of the notification -- "
              << "not emitting notification";
     return;
   }
-  if (notification_data.GetChangedTypes().Empty()) {
-    DVLOG(1) << "No changed types -- not emitting notification";
+  const ModelTypeSet types_to_notify =
+      Intersection(enabled_types_, notification_data.GetChangedTypes());
+  if (types_to_notify.Empty()) {
+    DVLOG(1) << "No enabled and changed types -- not emitting notification";
     return;
   }
   const ModelTypePayloadMap& type_payloads =
-      ModelTypePayloadMapFromEnumSet(
-          notification_data.GetChangedTypes(), std::string());
+      ModelTypePayloadMapFromEnumSet(types_to_notify, std::string());
   FOR_EACH_OBSERVER(SyncNotifierObserver, observer_list_,
                     OnIncomingNotification(type_payloads, REMOTE_NOTIFICATION));
 }
 
 void P2PNotifier::SendNotificationDataForTest(
     const P2PNotificationData& notification_data) {
   DCHECK(thread_checker_.CalledOnValidThread());
   SendNotificationData(notification_data);
 }
 
 void P2PNotifier::SendNotificationData(
     const P2PNotificationData& notification_data) {
   DCHECK(thread_checker_.CalledOnValidThread());
   notifier::Notification notification;
   notification.channel = kSyncP2PNotificationChannel;
   notification.data = notification_data.ToString();
   DVLOG(1) << "Sending XMPP notification: " << notification.ToString();
   push_client_->SendNotification(notification);
 }
 
 }  // namespace syncer