Implement the `RegExp.prototype.flags` getter

src/harmony-regexp.js

+// Copyright 2014 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.
+
+var $RegExp = global.RegExp;
+
+// -------------------------------------------------------------------
+
+function ExtendRegExpPrototype() {
+  var NoOpSetter = function(ignored) {};
+
+
+  // ES6 draft 12-06-13, section 21.2.5.3
+  // + https://bugs.ecmascript.org/show_bug.cgi?id=3423
+  var RegExpGetFlags = function() {

[arv (Not doing code reviews), 2014/12/10 02:54:50]

Move this out of ExtendRegExpPrototype.

+    if (!IS_SPEC_OBJECT(this)) {
+      throw MakeTypeError('home_object_non_object',

[Dmitry Lomov (no reviews), 2014/12/09 23:39:13]

Wrong error message. 

+                          'RegExp.prototype.flags',
+                          [%ToString(this)]);
+    }
+    var result = '';
+    if (this.global) result += 'g';
+    if (this.ignoreCase) result += 'i';
+    if (this.multiline) result += 'm';
+    if (this.unicode) result += 'u';
+    if (this.sticky) result += 'y';
+    return result;
+  };
+
+  %DefineAccessorPropertyUnchecked($RegExp.prototype, 'flags', RegExpGetFlags,

[Dmitry Lomov (no reviews), 2014/12/09 23:39:13]

You should pass 'undefined' here instead of NoOpSetter.
Regexp.prototype.flags do not have a setter.

+                                   NoOpSetter, DONT_DELETE);
+  %SetNativeFlag(RegExpGetFlags);
+}
+
+ExtendRegExpPrototype();