Create stub jingle library for iOS.

jingle/notifier/base/gaia_constants.h

Index: jingle/notifier/base/gaia_constants.h
diff --git a/jingle/notifier/listener/push_client_observer.cc b/jingle/notifier/base/gaia_constants.h
similarity index 53%
copy from jingle/notifier/listener/push_client_observer.cc
copy to jingle/notifier/base/gaia_constants.h
index 04a877b52c78ec897a02a97d3281007731bd965b..fe2c993bd2ed28eff98e527bc017faa0519f5a4e 100644
--- a/jingle/notifier/listener/push_client_observer.cc
+++ b/jingle/notifier/base/gaia_constants.h
@@ -2,10 +2,13 @@
 // 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"
+#ifndef JINGLE_NOTIFIER_BASE_GAIA_CONSTANTS_H_
+#define JINGLE_NOTIFIER_BASE_GAIA_CONSTANTS_H_
 
 namespace notifier {
 
-PushClientObserver::~PushClientObserver() {}
+extern const char kDefaultGaiaAuthMechanism[];
 
 }  // namespace notifier
+
+#endif  // JINGLE_NOTIFIER_BASE_GAIA_CONSTANTS_H_