[Chromoting] Enable jscompile for webapp unittests.

remoting/webapp/unittests/xmpp_stream_parser_unittest.js

Index: remoting/webapp/unittests/xmpp_stream_parser_unittest.js
diff --git a/remoting/webapp/unittests/xmpp_stream_parser_unittest.js b/remoting/webapp/unittests/xmpp_stream_parser_unittest.js
index 21a972e9bd0ba7f90137005bb2e2723b33cdd089..ec6cc4530a7a9e2568bea9cc7ee12cc270e8de4b 100644
--- a/remoting/webapp/unittests/xmpp_stream_parser_unittest.js
+++ b/remoting/webapp/unittests/xmpp_stream_parser_unittest.js
@@ -6,14 +6,20 @@
 
 'use strict';
 
+/** @type {Function} */
 var onStanzaStr = null;
-var onError = null;
+
+/** @type {function(string):void} */
+var onError = function(msg) {};
+
+/** @type {remoting.XmppStreamParser} */
 var parser = null;
 
 module('XmppStreamParser', {
   setup: function() {
     onStanzaStr = sinon.spy();
-    onError = sinon.spy();
+    onError = /** @type {function(string):void} */ (sinon.spy());
+    /** @param {Element} stanza */
     function onStanza(stanza) {
       onStanzaStr(new XMLSerializer().serializeToString(stanza));
     }