Removed Polymer from Observatory deps

packages/web_components/lib/polyfill.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.
 
 /** Dart APIs for interacting with the JavaScript Custom Elements polyfill. */
 library web_components.polyfill;
 
 import 'dart:async';
 import 'dart:html';
 import 'dart:js' as js;
@@ skipping 20 matching lines @@
 // have native document.register and therefore the browser took care of it.
 // Otherwise return false, including the case where we can't find the polyfill.
 bool get _isReady {
   // If we don't have dart:js, assume things are ready
   if (js.context == null) return true;
 
   var customElements = js.context['CustomElements'];
   if (customElements == null) {
     // Return true if native document.register, otherwise false.
     // (Maybe the polyfill isn't loaded yet. Wait for it.)
-    return document.supportsRegister;
+    return document.supportsRegisterElement;
   }
 
   return customElements['ready'] == true;
 }
 
 /**
  * *Note* this API is primarily intended for tests. In other code it is better
  * to write it in a style that works with or without the polyfill, rather than
  * using this method.
  *
  * Synchronously trigger evaluation of pending lifecycle events, which otherwise
  * need to wait for a [MutationObserver] to signal the changes in the polyfill.
  * This method can be used to resolve differences in timing between native and
  * polyfilled custom elements.
  */
 void customElementsTakeRecords([Node node]) {
   var customElements = js.context['CustomElements'];
   if (customElements == null) return;
   customElements.callMethod('takeRecords', [node]);
 }