[Sync] Fix race condition in P2PNotifier with sending notifications

jingle/notifier/listener/notification_defines.cc

Index: jingle/notifier/listener/notification_defines.cc
diff --git a/jingle/notifier/listener/notification_defines.cc b/jingle/notifier/listener/notification_defines.cc
new file mode 100644
index 0000000000000000000000000000000000000000..61b099a3a2bd9db11f2fedaf8d2adce66c0cac33
--- /dev/null
+++ b/jingle/notifier/listener/notification_defines.cc
@@ -0,0 +1,13 @@
+// Copyright (c) 2011 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 "jingle/notifier/listener/notification_defines.h"
+
+namespace notifier {
+
+std::string Notification::ToString() const {
+  return "{ channel: \"" + channel + "\", data: \"" + data + "\" }";
+}
+
+}  // namespace notifier