dart2js: fix method setup on mixin classes in the new emitter.

pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart

 // Copyright (c) 2014, 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.
 
 library dart2js.new_js_emitter.model_emitter;
 
 import '../../dart2jslib.dart' show Compiler;
 import '../../dart_types.dart' show DartType;
 import '../../js/js.dart' as js;
 import '../../js_backend/js_backend.dart' show
@@ skipping 767 matching lines @@
   #parseFunctionDescriptor;
 
   function compileConstructor(name, descriptor) {
     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, descriptor[i + 1]);
+        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;
@@ skipping 88 matching lines @@
 
   var end = Date.now();
   print('Setup: ' + (end - start) + ' ms.');
 
   #main();  // Start main.
 
 }(Date.now(), #code)
 }""";
 
 }