ES6: Implement generator method shorthand

src/v8natives.js

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file relies on the fact that the following declarations have been made
 // in runtime.js:
 // var $Object = global.Object;
 // var $Boolean = global.Boolean;
 // var $Number = global.Number;
 // var $Function = global.Function;
@@ skipping 1740 matching lines @@
   }
 
   if (%FunctionIsArrow(func)) {
     return source;
   }
 
   var name = %FunctionNameShouldPrintAsAnonymous(func)
       ? 'anonymous'
       : %FunctionGetName(func);
 
-  // TODO(arv): Handle concise generator methods.
-
+  var isGenerator = %FunctionIsGenerator(func);
   var head = %FunctionIsConciseMethod(func)
-      ? ''
-      : %FunctionIsGenerator(func) ? 'function* ' : 'function ';
+      ? (isGenerator ? '*' : '')
+      : (isGenerator ? 'function* ' : 'function ');
   return head + name + source;
 }
 
 
 function FunctionToString() {
   return FunctionSourceString(this);
 }
 
 
 // ES5 15.3.4.5
@@ skipping 130 matching lines @@
   }
   if (!IS_SPEC_FUNCTION(method)) {
     throw MakeTypeError('not_iterable', [obj]);
   }
   var iterator = %_CallFunction(obj, method);
   if (!IS_SPEC_OBJECT(iterator)) {
     throw MakeTypeError('not_an_iterator', [iterator]);
   }
   return iterator;
 }