[Chromoting] Enable jscompile for webapp unittests.

remoting/webapp/base/js/ipc.js

Index: remoting/webapp/base/js/ipc.js
diff --git a/remoting/webapp/base/js/ipc.js b/remoting/webapp/base/js/ipc.js
index a940a28fc1b959a0c7d4b3f48c33c87eea55d8e9..f6dfd9c9feddd290cc82b7f50030f57bfb3c726f 100644
--- a/remoting/webapp/base/js/ipc.js
+++ b/remoting/webapp/base/js/ipc.js
@@ -145,8 +145,8 @@ base.Ipc.prototype.onMessage_ = function(message, sender, sendResponse) {
  *
  * @param {string} methodName
  * @param {...} var_args
- * @return A Promise that would resolve to the return value of the handler or
- *   reject if the handler throws an exception.
+ * @return {Promise} A Promise that would resolve to the return value of the
+ *   handler or reject if the handler throws an exception.
  */
 base.Ipc.invoke = function(methodName, var_args) {
   var params = Array.prototype.slice.call(arguments, 1);