anchor.diff:   * The mixin class for Polymer elements. It provides convenience features on top
    * of the custom elements web standard.
    */
  -abstract class Polymer implements Element {
  +abstract class Polymer implements Element, Observable {
     // Fully ported from revision:
     // https://github.com/Polymer/polymer/blob/4dc481c11505991a7c43228d3797d28f21267779
     //
  
positive.code:   //
    // Not yet ported:
    //   src/instance/style.js -- blocked on ShadowCSS.shimPolyfillDirectives
  
  
    // TODO(jmesserly): should this really be public?
    /** Regular expression that matches data-bindings. */
  
negative.code:   /** Locate nodes with id and store references to them in [$] hash. */
    void marshalNodeReferences(Node root) {
      if (root == null) return;
      for (var n in (root as dynamic).queryAll('[id]')) {
        $[n.id] = n;
      }
    }
  