[polymer] interop with polymer-element and polymer.js
[polymer] interop with polymer-element and polymer.js

* let polymer.js register polymer-element
* let polymer.js bootstrap for polymer.dart
* hook polymer-element's register, if it's a Dart class go down the Dart code path

building polymer.concat.js (debug only) requires https://github.com/Polymer/polymer-dev/pull/9

R=sigmund@google.com

Review URL: https://codereview.chromium.org//182193002

git-svn-id: 34d430745197549daf83b1f027ea5104cda4d1f7@33398 260f80e4-7a28-3924-810f-c04153c831b5

dart-archive/template-binding,dart-archive/template-binding,dart-archive/template-binding