[es6] Use the correct ToPrimitive in the Date Constructor.

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) {
 
 "use strict";
 
 %CheckIsBootstrapping();
 
 // -------------------------------------------------------------------
 // Imports
 
 var GlobalDate = global.Date;
 var GlobalObject = global.Object;
 var InternalArray = utils.InternalArray;
 var IsFinite;
 var MathAbs;
 var MathFloor;
 var ToNumber;
-var toPrimitiveSymbol = utils.ImportNow("to_primitive_symbol");
 var ToString;
 
 utils.Import(function(from) {
   IsFinite = from.IsFinite;
   MathAbs = from.MathAbs;
   MathFloor = from.MathFloor;
   ToNumber = from.ToNumber;
   ToString = from.ToString;
 });
 
@@ skipping 107 matching lines @@
 
   // ECMA 262 - 15.9.3
   var argc = %_ArgumentsLength();
   var value;
   if (argc == 0) {
     value = %DateCurrentTime();
     SET_UTC_DATE_VALUE(this, value);
   } else if (argc == 1) {
     if (IS_NUMBER(year)) {
       value = year;
+
     } else if (IS_STRING(year)) {
       // Probe the Date cache. If we already have a time value for the
       // given time, we re-use that instead of parsing the string again.
       CheckDateCacheCurrent();
       var cache = Date_cache;
       if (cache.string === year) {
         value = cache.time;
       } else {
         value = DateParse(year);
         if (!NUMBER_IS_NAN(value)) {
           cache.time = value;
           cache.string = year;
         }
       }
 
+    } else if (IS_DATE(year)) {
+      value = UTC_DATE_VALUE(year);
+
     } else {
-      // According to ECMA 262, no hint should be given for this
-      // conversion. However, ToPrimitive defaults to STRING_HINT for
-      // Date objects which will lose precision when the Date
-      // constructor is called with another Date object as its
-      // argument. We therefore use NUMBER_HINT for the conversion,
-      // which is the default for everything else than Date objects.
-      // This makes us behave like KJS and SpiderMonkey.
-      var time = $toPrimitive(year, NUMBER_HINT);
+      var time = TO_PRIMITIVE(year);
       value = IS_STRING(time) ? DateParse(time) : ToNumber(time);
     }
     SET_UTC_DATE_VALUE(this, value);
   } else {
     year = ToNumber(year);
     month = ToNumber(month);
     date = argc > 2 ? ToNumber(date) : 1;
     hours = argc > 3 ? ToNumber(hours) : 0;
     minutes = argc > 4 ? ToNumber(minutes) : 0;
     seconds = argc > 5 ? ToNumber(seconds) : 0;
@@ skipping 695 matching lines @@
   "toUTCString", DateToUTCString,
   "getYear", DateGetYear,
   "setYear", DateSetYear,
   "toISOString", DateToISOString,
   "toJSON", DateToJSON
 ]);
 
 %InstallToContext(["create_date_fun", CreateDate]);
 
 })