[es6] Implement Date.prototype[@@toPrimitive] as C++ builtin.

src/date.js

 // Copyright 2006-2008 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 $createDate;
 
 // -------------------------------------------------------------------
 
 (function(global, utils) {
 
@@ skipping 347 matching lines @@
 
 // ECMA 262 - 15.9.5.7
 function DateToLocaleTimeString() {
   CHECK_DATE(this);
   var t = UTC_DATE_VALUE(this);
   if (NUMBER_IS_NAN(t)) return kInvalidDate;
   return TimeString(this);
 }
 
 
-// 20.3.4.45 Date.prototype [ @@toPrimitive ] ( hint )
-function DateToPrimitive(hint) {
-  if (!IS_SPEC_OBJECT(this)) {
-    throw MakeTypeError(kIncompatibleMethodReceiver,
-                        "Date.prototype [ @@toPrimitive ]", this);
-  }
-  if (hint === "default") {
-    hint = "string";
-  } else if (hint !== "number" && hint !== "string") {
-    throw MakeTypeError(kInvalidHint, hint);
-  }
-  return %OrdinaryToPrimitive(this, hint);
-}
-
-
 // ECMA 262 - 15.9.5.8
 function DateValueOf() {
   CHECK_DATE(this);
   return UTC_DATE_VALUE(this);
 }
 
 
 // ECMA 262 - 15.9.5.9
 function DateGetTime() {
   CHECK_DATE(this);
@@ skipping 448 matching lines @@
 
 // Set up non-enumerable properties of the Date object itself.
 utils.InstallFunctions(GlobalDate, DONT_ENUM, [
   "UTC", DateUTC,
   "parse", DateParse,
   "now", DateNow
 ]);
 
 // Set up non-enumerable constructor property of the Date prototype object.
 %AddNamedProperty(GlobalDate.prototype, "constructor", GlobalDate, DONT_ENUM);
-utils.SetFunctionName(DateToPrimitive, toPrimitiveSymbol);
-%AddNamedProperty(GlobalDate.prototype, toPrimitiveSymbol, DateToPrimitive,
-                  DONT_ENUM | READ_ONLY);
 
 // Set up non-enumerable functions of the Date prototype object and
 // set their names.
 utils.InstallFunctions(GlobalDate.prototype, DONT_ENUM, [
   "toString", DateToString,
   "toDateString", DateToDateString,
   "toTimeString", DateToTimeString,
   "toLocaleString", DateToLocaleString,
   "toLocaleDateString", DateToLocaleDateString,
   "toLocaleTimeString", DateToLocaleTimeString,
@@ skipping 35 matching lines @@
   "toUTCString", DateToUTCString,
   "getYear", DateGetYear,
   "setYear", DateSetYear,
   "toISOString", DateToISOString,
   "toJSON", DateToJSON
 ]);
 
 %InstallToContext(["create_date_fun", CreateDate]);
 
 })