Improve apps v2 upgrade UX

remoting/webapp/base/js/base.js

 // Copyright 2014 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.
 
 /**
  * @fileoverview
  * A module that contains basic utility components and methods for the
  * chromoting project
  *
  */
@@ skipping 252 matching lines @@
       function() {
         return Promise.reject();
       },
       /** @return {Promise} */
       function() {
         return Promise.resolve();
       });
 };
 
 /**
+ * Converts a |method| with callbacks into a Promise.
+ *
+ * @param {Function} method
+ * @param {Array} params
+ * @param {*=} opt_context
+ * @param {boolean=} opt_hasErrorHandler whether the method has an error handler
+ * @return {Promise}
+ */
+base.Promise.as = function(method, params, opt_context, opt_hasErrorHandler) {
+  return new Promise(function(resolve, reject) {
+    params.push(resolve);
+    if (opt_hasErrorHandler) {
+      params.push(reject);
+    }
+    try {
+      method.apply(opt_context, params);
+    } catch (/** @type {*} */ e) {
+      reject(e);
+    }
+  });
+};
+
+/**
  * A mixin for classes with events.
  *
  * For example, to create an alarm event for SmokeDetector:
  * functionSmokeDetector() {
  *    this.defineEvents(['alarm']);
  * };
  * base.extend(SmokeDetector, base.EventSource);
  *
  * To fire an event:
  * SmokeDetector.prototype.onCarbonMonoxideDetected = function() {
@@ skipping 155 matching lines @@
  * @return {Object|undefined} The decoded object, or undefined if the string
  *     cannot be parsed.
  */
 base.jsonParseSafe = function(jsonString) {
   try {
     return /** @type {Object} */ (JSON.parse(jsonString));
   } catch (err) {
     return undefined;
   }
 }