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

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

Index: chrome/test/data/webui/settings/test_util.js
diff --git a/chrome/test/data/webui/settings/test_util.js b/chrome/test/data/webui/settings/test_util.js
index d6cf3f7b5ca9500fcd759e263b082a7c71446447..4ed76509bed5abefcacfc764012cfe98cbf363cb 100644
--- a/chrome/test/data/webui/settings/test_util.js
+++ b/chrome/test/data/webui/settings/test_util.js
@@ -12,7 +12,12 @@ cr.define('test_util', function() {
    * @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) {