Add ES2015 RegExp full subclassing semantics behind a flag

src/js/i18n.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.
 
 // ECMAScript 402 API implementation.
 
 /**
  * Intl object is a single object that has some named properties,
  * all of which are constructors.
  */
@@ skipping 18 matching lines @@
 var GlobalNumber = global.Number;
 var GlobalRegExp = global.RegExp;
 var GlobalString = global.String;
 var MakeError;
 var MakeRangeError;
 var MakeTypeError;
 var MathFloor;
 var ObjectDefineProperties = utils.ImportNow("ObjectDefineProperties");
 var ObjectDefineProperty = utils.ImportNow("ObjectDefineProperty");
 var ObjectHasOwnProperty = utils.ImportNow("ObjectHasOwnProperty");
+var OverrideFunction = utils.OverrideFunction;
 var patternSymbol = utils.ImportNow("intl_pattern_symbol");
 var RegExpTest;
 var resolvedSymbol = utils.ImportNow("intl_resolved_symbol");
 var SetFunctionName = utils.SetFunctionName;
 var StringIndexOf;
 var StringLastIndexOf;
 var StringMatch;
 var StringReplace;
 var StringSplit;
 var StringSubstr;
@@ skipping 14 matching lines @@
   StringLastIndexOf = from.StringLastIndexOf;
   StringMatch = from.StringMatch;
   StringReplace = from.StringReplace;
   StringSplit = from.StringSplit;
   StringSubstr = from.StringSubstr;
   StringSubstring = from.StringSubstring;
 });
 
 // Utilities for definitions
 
-function OverrideFunction(object, name, f) {
-  %CheckIsBootstrapping();
-  ObjectDefineProperty(object, name, { value: f,
-                                       writeable: true,
-                                       configurable: true,
-                                       enumerable: false });
-  %FunctionSetName(f, name);
-  %FunctionRemovePrototype(f);
-  %SetNativeFlag(f);
-}
-
 function InstallFunction(object, name, func) {
   InstallFunctions(object, DONT_ENUM, [name, func]);
 }
 
 
 function InstallConstructor(object, name, func) {
   %CheckIsBootstrapping();
   SetFunctionName(func, name);
   %AddNamedProperty(object, name, func, DONT_ENUM);
   %SetNativeFlag(func);
@@ skipping 2054 matching lines @@
     }
 
     var locales = arguments[0];
     var options = arguments[1];
     return toLocaleDateTime(
         this, locales, options, 'time', 'time', 'dateformattime');
   }
 );
 
 })