fix build due to mdv -> template_binding rename

pkg/custom_element/lib/custom_element.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.
 
 /**
  * Custom DOM elements.
  *
  * This library provides access to the Polymer project's
  * [Custom Elements]
  * (http://www.polymer-project.org/platform/custom-elements.html)
  * API, which lets you define your own elements. With custom elements, you
  * associate code with custom tag names, and then use those custom tag names
  * as you would any standard tag. For more information, see the
  * [Polymer.dart homepage](https://www.dartlang.org/polymer-dart/) and its
  * [custom element example]
  * (https://www.dartlang.org/polymer-dart/#custom-elements).
  */
 library custom_element;
 
 import 'dart:async';
 import 'dart:html';
-import 'package:mdv/mdv.dart' as mdv;
 import 'package:meta/meta.dart';
 import 'src/custom_tag_name.dart';
 
 part 'src/attribute_map.dart';
 
 // TODO(jmesserly): replace with a real custom element polyfill.
 // This is just something temporary.
 /**
  * *Warning*: this implementation is a work in progress. It only implements
  * the specification partially.
  *
  * Registers a custom HTML element with [localName] and the associated
  * constructor. This will ensure the element is detected and
  *
  * See the specification at:
  * <https://dvcs.w3.org/hg/webcomponents/raw-file/tip/spec/custom/index.html>
  */
 void registerCustomElement(String localName, CustomElement create()) {
   if (_customElements == null) {
     _customElements = {};
-    mdv.instanceCreated.add(initCustomElements);
     // TODO(jmesserly): use MutationObserver to watch for inserts?
   }
 
   if (!isCustomTag(localName)) {
     throw new ArgumentError('$localName is not a valid custom element name, '
         'it should have at least one dash and not be a reserved name.');
   }
 
   if (_customElements.containsKey(localName)) {
     throw new ArgumentError('custom element $localName already registered.');
@@ skipping 593 matching lines @@
       for (var removed in record.removedNodes) {
         if (identical(node, removed)) {
           observer.disconnect();
           element.removed();
           return;
         }
       }
     }
   }).observe(element.parentNode, childList: true);
 }