I found this issues:
https://code.google.com/p/dart/issues/detail?id=14098 This is not the post I talked about in my comment.
https://code.google.com/p/dart/issues/detail?id=13758 The linked discussion in this issue could be the post I remembered
the TodoMVC is a Dart demo project (https://www.dartlang.org/samples/) that uses some Polymer.js polymer_elements see source in lib-elements directory
As mentioned in my comment alternatively you could use the Dart port of polymer_elements and polymer_ui_elements