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..38cc5cdac4fe3b54ac97a0f76aef7ec3a0d7bc6b 100644
--- a/chrome/test/data/webui/polymer_browser_test_base.js
+++ b/chrome/test/data/webui/polymer_browser_test_base.js
@@ -90,12 +90,9 @@ PolymerTest.prototype = {
 
     // Import Polymer and iron-test-helpers before running tests.
     suiteSetup(function() {
-      var promises = [];
-      if (typeof Polymer != 'function') {

[michaelpg, 2016/04/05 00:49:42]

maybe keep this as 
    if (!Polymer) {

-        promises.push(
-            PolymerTest.importHtml(
-                'chrome://resources/polymer/v1_0/polymer/polymer.html'));
-      }
+      var promises = [
+        PolymerTest.importHtml('chrome://resources/html/polymer.html'),

[michaelpg, 2016/04/05 00:49:42]

this assumes the page being tested doesn't load
    <script src="chrome://resources/js/polymer_config.js"></script>

which is untrue for pages that don't use chrome://resources/html/polymer.html,
like MediaRouter (this will cause MediaRouterElementsBrowserTest to fail)

[Dan Beam, 2016/04/05 01:38:58]

why doesn't media router stuff use polymer.html?

+      ];
       if (typeof MockInteractions != 'object') {
         // Avoid importing the HTML file because iron-test-helpers assumes it is
         // not being imported separately alongside a vulcanized Polymer.