Fix regression in JSON serialization of RegExps.

src/date.js

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 966 matching lines @@
 
 function PadInt(n, digits) {
   if (digits == 1) return n;
   return n < MathPow(10, digits - 1) ? '0' + PadInt(n, digits - 1) : n;
 }
 
 
 function DateToISOString() {
   var t = DATE_VALUE(this);
   if (NUMBER_IS_NAN(t)) return kInvalidDate;
-  return this.getUTCFullYear() + '-' + PadInt(this.getUTCMonth() + 1, 2) +
-      '-' + PadInt(this.getUTCDate(), 2) + 'T' + PadInt(this.getUTCHours(), 2) +
-      ':' + PadInt(this.getUTCMinutes(), 2) + ':' + PadInt(this.getUTCSeconds(), 2) +
+  return this.getUTCFullYear() + 
+      '-' + PadInt(this.getUTCMonth() + 1, 2) +
+      '-' + PadInt(this.getUTCDate(), 2) + 
+      'T' + PadInt(this.getUTCHours(), 2) +
+      ':' + PadInt(this.getUTCMinutes(), 2) + 
+      ':' + PadInt(this.getUTCSeconds(), 2) +
       '.' + PadInt(this.getUTCMilliseconds(), 3) +
       'Z';
 }
 
 
 function DateToJSON(key) {
-  return CheckJSONPrimitive(this.toISOString());
+  var o = ToObject(this);
+  var tv = DefaultNumber(o);
+  if (IS_NUMBER(tv) && !$isFinite(tv)) { 
+    return null; 
+  }
+  return o.toISOString();
 }
 
 
 // -------------------------------------------------------------------
 
 function SetupDate() {
   // Setup non-enumerable properties of the Date object itself.
   InstallFunctions($Date, DONT_ENUM, $Array(
     "UTC", DateUTC,
     "parse", DateParse,
@@ skipping 49 matching lines @@
     "toGMTString", DateToGMTString,
     "toUTCString", DateToUTCString,
     "getYear", DateGetYear,
     "setYear", DateSetYear,
     "toISOString", DateToISOString,
     "toJSON", DateToJSON
   ));
 }
 
 SetupDate();