Make ClosureMirror handle instances of user-defined classes that implement call.

sdk/lib/mirrors/mirrors.dart

 // Copyright (c) 2012, 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.
 
 // For the purposes of the mirrors library, we adopt a naming
 // convention with respect to getters and setters.  Specifically, for
 // some variable or field...
 //
 //   var myField;
 //
@@ skipping 872 matching lines @@
    */
   TypeMirror get returnType;
 
   /**
    * Returns a list of the parameter types of the reflectee.
    */
   List<ParameterMirror> get parameters;
 
   /**
    * A mirror on the [:call:] method for the reflectee.
-   *
-   * TODO(turnidge): What is this and what is it for?
    */
   MethodMirror get callMethod;
 }
 
 /**
  * A [TypeVariableMirror] represents a type parameter of a generic
  * type.
  */
 abstract class TypeVariableMirror extends TypeMirror {
   /**
@@ skipping 403 matching lines @@
    *
    * When used as metadata on an import of "dart:mirrors", this metadata does
    * not apply to the library in which the annotation is used, but instead
    * applies to the other libraries (all libraries if "*" is used).
    */
   final override;
 
   const MirrorsUsed(
       {this.symbols, this.targets, this.metaTargets, this.override});
 }