introduce web_components pkg for consolidated polyfills

tests/html/utils.dart

Index: tests/html/utils.dart
diff --git a/tests/html/utils.dart b/tests/html/utils.dart
index 9b469b1f20c3958c2e0972729789fbc39d0fd8d7..f8d2e6dc8a23aebaed1b6256443d25b9c13073d7 100644
--- a/tests/html/utils.dart
+++ b/tests/html/utils.dart
@@ -5,6 +5,7 @@ import 'dart:html';
 import 'dart:js' as js;
 import 'dart:typed_data';
 import 'package:unittest/unittest.dart';
+export 'package:web_components/polyfill.dart';
 
 /**
  * Verifies that [actual] has the same graph structure as [expected].
@@ -161,20 +162,6 @@ void validateNodeTree(Node a, Node b, [String path = '']) {
   }
 }
 
-Future loadCustomElementPolyfill() {
-  if (!document.supportsRegister) {
-    var script = new ScriptElement()
-        ..src = '/packages/custom_element/custom-elements.debug.js';
-    document.head.append(script);
-    return document.on['WebComponentsReady'].first;
-  }
-  return new Future.value();
-}
-
-Future loadPolyfills() {
-  return loadCustomElementPolyfill();
-}
-
 /**
  * Upgrade all custom elements in the subtree which have not been upgraded.
  *