MD Downloads: fix vulcanize issues by excluding higher up in the dependency tree

chrome/test/data/webui/polymer_browser_test_base.js

Index: chrome/test/data/webui/polymer_browser_test_base.js
diff --git a/chrome/test/data/webui/polymer_browser_test_base.js b/chrome/test/data/webui/polymer_browser_test_base.js
index bab6405dd7878eadc1873ab6d0d87a80073ef453..f3a9b167347936ce9c4460a2b71acde3f97badca 100644
--- a/chrome/test/data/webui/polymer_browser_test_base.js
+++ b/chrome/test/data/webui/polymer_browser_test_base.js
@@ -91,10 +91,9 @@ PolymerTest.prototype = {
     // Import Polymer and iron-test-helpers before running tests.
     suiteSetup(function() {
       var promises = [];
-      if (typeof Polymer != 'function') {
+      if (!window.Polymer) {
         promises.push(
-            PolymerTest.importHtml(
-                'chrome://resources/polymer/v1_0/polymer/polymer.html'));
+            PolymerTest.importHtml('chrome://resources/html/polymer.html'));
       }
       if (typeof MockInteractions != 'object') {
         // Avoid importing the HTML file because iron-test-helpers assumes it is