[builtins] Migrate String.fromCharCode to C++.

src/js/string.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.
 
 (function(global, utils) {
 
 %CheckIsBootstrapping();
 
 // -------------------------------------------------------------------
 // Imports
@@ skipping 522 matching lines @@
   return %StringTrim(TO_STRING(this), true, false);
 }
 
 function StringTrimRight() {
   CHECK_OBJECT_COERCIBLE(this, "String.prototype.trimRight");
 
   return %StringTrim(TO_STRING(this), false, true);
 }
 
 
-// ECMA-262, section 15.5.3.2
-function StringFromCharCode(_) {  // length == 1
-  "use strict";
-  var s = "";
-  var n = arguments.length;
-  for (var i = 0; i < n; ++i) {
-    s += %_StringCharFromCode(arguments[i] & 0xffff);
-  }
-  return s;
-}
-
-
 // ES6 draft, revision 26 (2014-07-18), section B.2.3.2.1
 function HtmlEscape(str) {
   return %_Call(StringReplace, TO_STRING(str), /"/g, "&quot;");
 }
 
 
 // ES6 draft, revision 26 (2014-07-18), section B.2.3.2
 function StringAnchor(name) {
   CHECK_OBJECT_COERCIBLE(this, "String.prototype.anchor");
   return "<a name=\"" + HtmlEscape(name) + "\">" + TO_STRING(this) +
@@ skipping 263 matching lines @@
     result += TO_STRING(raw[i]);
   }
 
   return result;
 }
 
 // -------------------------------------------------------------------
 
 // Set up the non-enumerable functions on the String object.
 utils.InstallFunctions(GlobalString, DONT_ENUM, [
-  "fromCharCode", StringFromCharCode,
   "fromCodePoint", StringFromCodePoint,
   "raw", StringRaw
 ]);
 
 // Set up the non-enumerable functions on the String prototype object.
 utils.InstallFunctions(GlobalString.prototype, DONT_ENUM, [
   "valueOf", StringValueOf,
   "toString", StringToString,
   "codePointAt", StringCodePointAt,
   "concat", StringConcat,
@@ skipping 44 matching lines @@
   to.StringLastIndexOf = StringLastIndexOf;
   to.StringMatch = StringMatchJS;
   to.StringReplace = StringReplace;
   to.StringSlice = StringSlice;
   to.StringSplit = StringSplitJS;
   to.StringSubstr = StringSubstr;
   to.StringSubstring = StringSubstring;
 });
 
 })