Introduce a BuiltinsConstructStub that sets up new.target and does a [[call]] per ES6 9.3.2

src/js/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.
 
 // -------------------------------------------------------------------
 
 (function(global, utils) {
 
 "use strict";
 
@@ skipping 114 matching lines @@
 // strings over and over again.
 var Date_cache = {
   // Cached time value.
   time: 0,
   // String input for which the cached time is valid.
   string: null
 };
 
 
 function DateConstructor(year, month, date, hours, minutes, seconds, ms) {
-  if (!%_IsConstructCall()) {
+  if (IS_UNDEFINED(new.target)) {
     // ECMA 262 - 15.9.2
     return %_Call(DateToString, new GlobalDate());
   }
 
   // ECMA 262 - 15.9.3
   var argc = %_ArgumentsLength();
   var value;
+  var result;
   if (argc == 0) {
     value = %DateCurrentTime();
-    SET_UTC_DATE_VALUE(this, value);
+    result = %NewObject(GlobalDate, new.target);
+    SET_UTC_DATE_VALUE(result, value);
   } else if (argc == 1) {
     if (IS_NUMBER(year)) {
       value = TimeClip(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 {
       var time = TO_PRIMITIVE(year);
       value = IS_STRING(time) ? DateParse(time) : TO_NUMBER(time);
     }
-    SET_UTC_DATE_VALUE(this, value);
+    result = %NewObject(GlobalDate, new.target);
+    SET_UTC_DATE_VALUE(result, value);
   } else {
     year = TO_NUMBER(year);
     month = TO_NUMBER(month);
     date = argc > 2 ? TO_NUMBER(date) : 1;
     hours = argc > 3 ? TO_NUMBER(hours) : 0;
     minutes = argc > 4 ? TO_NUMBER(minutes) : 0;
     seconds = argc > 5 ? TO_NUMBER(seconds) : 0;
     ms = argc > 6 ? TO_NUMBER(ms) : 0;
     year = (!NUMBER_IS_NAN(year) &&
             0 <= TO_INTEGER(year) &&
             TO_INTEGER(year) <= 99) ? 1900 + TO_INTEGER(year) : year;
     var day = MakeDay(year, month, date);
     var time = MakeTime(hours, minutes, seconds, ms);
     value = MakeDate(day, time);
-    SET_LOCAL_DATE_VALUE(this, value);
+    result = %NewObject(GlobalDate, new.target);
+    SET_LOCAL_DATE_VALUE(result, value);
   }
+
+  return result;
 }
 
 
 var WeekDays = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat'];
 var Months = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun',
               'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'];
 
 
 function TwoDigitString(value) {
   return value < 10 ? "0" + value : "" + value;
@@ skipping 676 matching lines @@
   "toUTCString", DateToUTCString,
   "getYear", DateGetYear,
   "setYear", DateSetYear,
   "toISOString", DateToISOString,
   "toJSON", DateToJSON
 ]);
 
 %InstallToContext(["create_date_fun", CreateDate]);
 
 })