introduce web_components pkg for consolidated polyfills

pkg/web_components/lib/polyfill.dart

Index: pkg/web_components/lib/polyfill.dart
diff --git a/pkg/custom_element/lib/polyfill.dart b/pkg/web_components/lib/polyfill.dart
similarity index 68%
rename from pkg/custom_element/lib/polyfill.dart
rename to pkg/web_components/lib/polyfill.dart
index 413d7d699a04f0e2acb736234d887a811520642e..36b1756a524099e3a16f6f8600ddd3a1d1b07f3a 100644
--- a/pkg/custom_element/lib/polyfill.dart
+++ b/pkg/web_components/lib/polyfill.dart
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 /** Dart APIs for interacting with the JavaScript Custom Elements polyfill. */
-library custom_element.polyfill;
+library web_components.polyfill;
 
 import 'dart:async';
 import 'dart:html';
@@ -17,6 +17,7 @@ import 'dart:js' as js;
  * while parsing the HTML document, but the custom element polyfill cannot,
  * so it completes this future once all elements are upgraded.
  */
+// TODO(jmesserly): rename to webComponentsReady to match the event?
 Future customElementsReady = () {
   if (_isReady) return new Future.value();
 
@@ -44,20 +45,13 @@ bool get _isReady {
 }
 
 /**
- * Loads `custom-elements.debug.js` or `custom-elements.min.js` by adding the
- * script tag to the page. Returns a future that completes when custom elements
- * are ready (equivalent to [customElementsReady]).
- *
- * Normally you should add this to your HTML file
- * (the Polymer package will do this automatically), but loading dynamically
- * can be useful for scenarios such as tests.
+ * Pump custom events polyfill events. This can be used to trigger
+ * evaluation of pending lifecycle events, which otherwise need to wait for a
+ * [MutationObserver] to signal the changes in the polyfill.
  */
-Future loadCustomElementPolyfill() {
-  if (!document.supportsRegister && !js.context.hasProperty('CustomElements')) {
-    var script = new ScriptElement()
-        ..src = '/packages/custom_element/custom-elements.debug.js';
-    document.head.append(script);
-    return document.on['WebComponentsReady'].first;
+void customElementsTakeRecords() {

[blois, 2014/02/08 01:37:02]

This should only really be used by unittests, would be good to either give it a
very explicit doc comment that it's for TESTS ONLY or move it to a separate
file.

[Jennifer Messerly, 2014/02/10 22:17:11]

Just checking: it's not possible an application could need this to resolve a
behavior difference between polyfill and non-polyfill? e.g.
https://groups.google.com/d/msg/polymer-dev/Df55skoYYNE/z69H9Up7z28J

I will definitely clarify the doc comment that it should not be necessary in
almost all cases.

+  var customElements = js.context['CustomElements'];
+  if (customElements != null) {
+    customElements.callMethod('takeRecords');
   }
-  return new Future.value();
 }