Introduce NUMBER_IS_FINITE macro to avoid ToNumber() conversion.

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 982 matching lines @@
       ':' + PadInt(this.getUTCMinutes(), 2) + 
       ':' + PadInt(this.getUTCSeconds(), 2) +
       '.' + PadInt(this.getUTCMilliseconds(), 3) +
       'Z';
 }
 
 
 function DateToJSON(key) {
   var o = ToObject(this);
   var tv = DefaultNumber(o);
-  if (IS_NUMBER(tv) && !$isFinite(tv)) { 
+  if (IS_NUMBER(tv) && !NUMBER_IS_FINITE(tv)) { 
     return null; 
   }
   return o.toISOString();
 }
 
 
 function ResetDateCache() {
 
   // Reset the local_time_offset:
   local_time_offset = %DateLocalTimeOffset();
@@ skipping 85 matching lines @@
     "toGMTString", DateToGMTString,
     "toUTCString", DateToUTCString,
     "getYear", DateGetYear,
     "setYear", DateSetYear,
     "toISOString", DateToISOString,
     "toJSON", DateToJSON
   ));
 }
 
 SetupDate();