anchor.diff:  
   import '../js_emitter.dart' show NativeGenerator, buildTearOffCode;
   import '../model.dart';
  -
   
   
   class ModelEmitter {
  
positive.code:     descriptor = compile(name, descriptor);
      var prototype = determinePrototype(descriptor);
      var constructor;
      // $mixinFormatDescription.
      if (typeof descriptor[2] !== 'function') {
        constructor = compileMixinConstructor(name, prototype, descriptor);
        for (var i = 4; i < descriptor.length; i += 2) {
          parseFunctionDescriptor(prototype, descriptor[i], descriptor[i + 1]);
        }
      } else {
        constructor = descriptor[2];
        for (var i = 3; i < descriptor.length; i += 2) {
          parseFunctionDescriptor(prototype, descriptor[i], descriptor[i + 1]);
        }
      }
      constructor.builtin\$cls = name;  // Needed for RTI.
      constructor.prototype = prototype;
      prototype[#operatorIsPrefix + name] = constructor;
  
negative.code:   // This string should be referenced wherever JavaScript code makes assumptions
    // on the mixin format.
    static final String mixinFormatDescription =
        "Mixins have a reference to their mixin class at the place of the usual"
        "constructor. If they are instantiated the constructor follows the"
        "reference.";
  
    js.Expression emitClass(Class cls) {
      List elements = [js.string(cls.superclassName),
  