Create stub jingle library for iOS.

jingle/notifier/base/gaia_constants.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 "jingle/notifier/listener/push_client_observer.h"
+#include "jingle/notifier/base/gaia_constants.h"
 
 namespace notifier {
 
-PushClientObserver::~PushClientObserver() {}
+namespace gaia_constants {
+
+// By default use a Google cookie auth mechanism.
+const char kDefaultAuthMechanism[] = "X-GOOGLE-TOKEN";
+
+}  // namespace gaia_constants
 
 }  // namespace notifier