Add Polymer tests for cr-settings-prefs

chrome/test/data/webui/polymer_browser_test_base.js

 // Copyright 2015 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 Framework for running JavaScript tests of Polymer elements.
  */
 
 /**
  * Test fixture for Polymer element testing.
@@ skipping 77 matching lines @@
  */
 PolymerTest.getLibraries = function(basePath) {
   // Ensure basePath ends in '/'.
   if (basePath.length && basePath[basePath.length - 1] != '/')
     basePath += '/';
 
   return PolymerTest.prototype.extraLibraries.map(function(library) {
     return basePath + library;
   });
 };
+
+/**
+ * Allows chaining asynchronous function to avoid having to write nested
+ * Promises or setTimeouts.
+ * Example: PolymerTest.async(fn1).async(fn2).async(fn3).async(done);
+ */
+PolymerTest.async = function(fn) {
+  // Wrap the asynchronous call to |fn| in a Promise.
+  var p = new Promise(function(resolve, reject) {
+    setTimeout(function() {
+      fn.call();
+      resolve();
+    });
+  });
+  // Return a helper function of the same name which adds this function to the
+  // Promise chain.
+  return {
+    async: function(fn) {
+      p.then(function() {
+        return PolymerTest.async(fn);

[michaelpg, 2015/09/08 06:26:59]

this doesn't quite work. what I actually want is something like
https://codereview.chromium.org/1333473002/diff/20001/chrome/test/data/webui/...
(not ready for review)

[michaelpg, 2015/09/11 20:14:38]

Ignore this comment, see new patch.

+      });
+    },
+  };
+};