Add @@iterator for generator objects

src/generator.js

 // Copyright 2013 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.
 
 "use strict";
 
 // This file relies on the fact that the following declarations have been made
 // in runtime.js:
 // var $Function = global.Function;
 
@@ skipping 14 matching lines @@
 
 function GeneratorObjectThrow(exn) {
   if (!IS_GENERATOR(this)) {
     throw MakeTypeError('incompatible_method_receiver',
                         ['[Generator].prototype.throw', this]);
   }
 
   return %_GeneratorThrow(this, exn);
 }
 
+function GeneratorObjectIterator() {
+  return this;
+}
+
 function GeneratorFunctionPrototypeConstructor(x) {
   if (%_IsConstructCall()) {
     throw MakeTypeError('not_constructor', ['GeneratorFunctionPrototype']);
   }
 }
 
 function GeneratorFunctionConstructor(arg1) {  // length == 1
   var source = NewFunctionString(arguments, 'function*');
   var global_receiver = %GlobalReceiver(global);
   // Compile the string in the constructor and not a helper so that errors
   // appear to come from here.
   var f = %_CallFunction(global_receiver, %CompileString(source, true));
   %FunctionMarkNameShouldPrintAsAnonymous(f);
   return f;
 }
 
 
 function SetUpGenerators() {
   %CheckIsBootstrapping();
   var GeneratorObjectPrototype = GeneratorFunctionPrototype.prototype;
   InstallFunctions(GeneratorObjectPrototype,
                    DONT_ENUM | DONT_DELETE | READ_ONLY,
                    ["next", GeneratorObjectNext,
                     "throw", GeneratorObjectThrow]);
+  %SetProperty(GeneratorObjectPrototype, symbolIterator, GeneratorObjectIterator,
+      DONT_ENUM | DONT_DELETE | READ_ONLY);
   %SetProperty(GeneratorObjectPrototype, "constructor",
                GeneratorFunctionPrototype, DONT_ENUM | DONT_DELETE | READ_ONLY);
   %SetPrototype(GeneratorFunctionPrototype, $Function.prototype);
   %SetCode(GeneratorFunctionPrototype, GeneratorFunctionPrototypeConstructor);
   %SetProperty(GeneratorFunctionPrototype, "constructor",
                GeneratorFunction, DONT_ENUM | DONT_DELETE | READ_ONLY);
   %SetPrototype(GeneratorFunction, $Function);
   %SetCode(GeneratorFunction, GeneratorFunctionConstructor);
 }
 
 SetUpGenerators();