[Chromoting] Enable jscompile for webapp unittests.

remoting/webapp/unittests/menu_button_unittest.js

Index: remoting/webapp/unittests/menu_button_unittest.js
diff --git a/remoting/webapp/unittests/menu_button_unittest.js b/remoting/webapp/unittests/menu_button_unittest.js
index 7337134d5ac6378487d26aa584fa060db90c28cf..1367b0da40b42c62eeae3573814eed7f58b26fe7 100644
--- a/remoting/webapp/unittests/menu_button_unittest.js
+++ b/remoting/webapp/unittests/menu_button_unittest.js
@@ -6,8 +6,11 @@
 
 'use strict';
 
+/** @type {(sinon.Spy|function():void)} */
 var onShow = null;
+/** @type {(sinon.Spy|function():void)} */
 var onHide = null;
+/** @type {remoting.MenuButton} */
 var menuButton = null;
 
 module('MenuButton', {
@@ -20,11 +23,12 @@ module('MenuButton', {
             '<li id="menu-option-1">Option 1</li>' +
           '</ul>' +
         '</span>';
-    onShow = sinon.spy();
-    onHide = sinon.spy();
+    onShow = /** @type {(sinon.Spy|function():void)} */ (sinon.spy());
+    onHide = /** @type {(sinon.Spy|function():void)} */ (sinon.spy());
     menuButton = new remoting.MenuButton(
         document.getElementById('menu-button-container'),
-        onShow, onHide);
+        /** @type {function():void} */ (onShow),
+        /** @type {function():void} */ (onHide));
   },
   teardown: function() {
     onShow = null;
@@ -87,4 +91,4 @@ test('select method should set/unset background image', function() {
   ok(style.backgroundImage == 'none');
 });
 
-}());
+}());