MD Settings: Fix and re-enable settings-main tests.

chrome/test/data/webui/settings/test_util.js

 // Copyright 2016 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.
 
 cr.define('test_util', function() {
   /**
    * Observes an HTML attribute and fires a promise when it matches a given
    * value.
    * @param {!HTMLElement} target
    * @param {string} attributeName
    * @param {*} attributeValue
    * @return {!Promise}
    */
   function whenAttributeIs(target, attributeName, attributeValue) {
-    function isDone() { return target[attributeName] === attributeValue; }
+    function isDone() {
+      // TODO(dpapad): Following line should check for an attribute, not a
+      // property, meaning target.getAttribute(attributeName). Fix this and
+      // update callers to pass an attribute value instead.
+      return target[attributeName] === attributeValue;
+    }
 
     return isDone() ? Promise.resolve() : new Promise(function(resolve) {
       new MutationObserver(function(mutations, observer) {
         for (var mutation of mutations) {
           assertEquals('attributes', mutation.type);
           if (mutation.attributeName == attributeName && isDone()) {
             observer.disconnect();
             resolve();
             return;
           }
@@ skipping 34 matching lines @@
     el1.addEventListener(property + '-changed', forwardChange.bind(null, el2));
     el2.addEventListener(property + '-changed', forwardChange.bind(null, el1));
   }
 
   return {
     eventToPromise: eventToPromise,
     fakeDataBind: fakeDataBind,
     whenAttributeIs: whenAttributeIs,
   };
 });