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) {

[Dan Beam, 2015/09/11 21:49:12]

initialize lastPromise_ to Promise.resolve(), remove if
(!PolymerTest.lastPromise_)

[michaelpg, 2015/09/13 03:01:05]

nice!

+  if (!PolymerTest.lastPromise_) {
+    PolymerTest.lastPromise_ = new Promise(function(resolve) {
+      setTimeout(fn);
+      setTimeout(resolve);
+    });
+  } else {
+    PolymerTest.lastPromise_ = PolymerTest.lastPromise_.then(function() {
+      return new Promise(function(resolve) {
+        setTimeout(fn);
+        setTimeout(resolve);
+      });
+    });
+  }
+  // Return a helper function of the same name which adds this function to the
+  // Promise chain.
+  return {
+    async: PolymerTest.async
+  };

[Dan Beam, 2015/09/11 21:49:12]

wat?  why not?

  return PolymerTest.lastPromise_;

so callers can chain?

[michaelpg, 2015/09/13 03:01:05]

Done. this was just sugar.

+};