anchor.diff:   * will construct a JavaScript Foo object with the parameter 42, invoke its
    * add method, and return a [Proxy] to a new Foo object whose x field is 84.
    *
  - * See [samples](http://dart-lang.github.com/js-interop/) for more examples
  + * See [samples](http://dart-lang.github.com/js-interop/example) for more examples
    * of usage.
    */
   
  
positive.code:   final _id;
  
    /**
     * Construct a [Proxy] to a new JavaScript object by invoking a (proxy to a)
     * JavaScript [constructor].  The arguments should be either
     * primitive values, DOM elements, or Proxies.
     */
  
negative.code:   });
  }
  
  // Evaluates a JavaScript string and return
  _js(String message) => _deserialize(_jsPortSync.callSync(_serialize(message)));
  
  /**
   * Returns a proxy to the global JavaScript context for this page.
   */
  Proxy get context {
    if (_depth == 0) throw 'Cannot get JavaScript context out of scope.';
  