Updating custom element test to only load polyfill when needed.

pkg/custom_element/test/custom_element_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library custom_element.test.custom_element_test;
 
 import 'dart:async';
 import 'dart:html';
 import 'package:custom_element/custom_element.dart';
 import 'package:unittest/html_config.dart';
 import 'package:unittest/unittest.dart';
 
 main() {
   useHtmlConfiguration();
 
-  // Load the MutationObserver polyfill.
-  HttpRequest.getString('/root_dart/pkg/mutation_observer/lib/'
-      'mutation_observer.js').then((code) {
-    document.head.children.add(new ScriptElement()..text = code);
+  setUp(() {
+    // Load the MutationObserver polyfill if needed.
+    if (!MutationObserver.supported) {
+      var script = new ScriptElement()
+          ..src =  '/packages/mutation_observer/mutation_observer.js';
+      document.head.append(script);
+      return script.onLoad.first;

[Jennifer Messerly, 2013/09/12 20:43:48]

Nice! This blocks the test until it loads? That was the bit I was missing, hence
used ".text" as a hacky workaround :)

Can enable CSP testing now with this fix?

[blois, 2013/09/12 21:23:13]

The setUp function handles Future return types just like tests. Primary benefit
of this approach is that mutation_observer.js appears in your sources list and
makes it easier to navigate.

CSP does not allow programmatic insertion of script tags, so no.

+    }
+  });
 
-    customElementTests();
-  });
-}
-
-customElementTests() {
   test('register creates the element and calls lifecycle methods', () {
     // Add element to the page.
     var element = new Element.html('<fancy-button>foo bar</fancy-button>',
         treeSanitizer: new NullTreeSanitizer());
     document.body.nodes.add(element);
 
     var xtag = null;
     registerCustomElement('fancy-button', () => xtag = new FancyButton());
     expect(xtag, isNotNull, reason: 'FancyButton was created');
     expect(element.xtag, xtag, reason: 'xtag pointer should be set');
@@ skipping 56 matching lines @@
     lifecycle.add('removed');
   }
 }
 
 /**
  * Sanitizer which does nothing.
  */
 class NullTreeSanitizer implements NodeTreeSanitizer {
   void sanitizeTree(Node node) {}
 }