[stubs] Port String.prototype.substring to TurboFan

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 17 matching lines @@
 var InternalArray = utils.InternalArray;
 var InternalRegExpMatch;
 var InternalRegExpReplace
 var ObjectHasOwnProperty = utils.ImportNow("ObjectHasOwnProperty");
 var OverrideFunction = utils.OverrideFunction;
 var patternSymbol = utils.ImportNow("intl_pattern_symbol");
 var resolvedSymbol = utils.ImportNow("intl_resolved_symbol");
 var SetFunctionName = utils.SetFunctionName;
 var StringIndexOf;
 var StringSubstr;
-var StringSubstring;
+var StringSubstring = GlobalString.prototype.substring;
 
 utils.Import(function(from) {
   ArrayJoin = from.ArrayJoin;
   ArrayPush = from.ArrayPush;
   InternalRegExpMatch = from.InternalRegExpMatch;
   InternalRegExpReplace = from.InternalRegExpReplace;
   StringIndexOf = from.StringIndexOf;
   StringSubstr = from.StringSubstr;
-  StringSubstring = from.StringSubstring;
 });
 
 // Utilities for definitions
 
 function InstallFunction(object, name, func) {
   InstallFunctions(object, DONT_ENUM, [name, func]);
 }
 
 
 function InstallConstructor(object, name, func) {
@@ skipping 2214 matching lines @@
   }
 );
 
 %FunctionRemovePrototype(FormatDateToParts);
 
 utils.Export(function(to) {
   to.FormatDateToParts = FormatDateToParts;
 });
 
 })