Introduce NUMBER_IS_FINITE macro to avoid ToNumber() conversion.

src/mirror-debugger.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 2351 matching lines @@
  * -Infinite the string representation "NaN", "Infinite" or "-Infinite"
  * (not including the quotes) is returned.
  *
  * @param {number} value The number value to convert to a protocol value.
  * @returns {number|string} Protocol value.
  */
 function NumberToJSON_(value) {
   if (isNaN(value)) {
     return 'NaN';
   }
-  if (!isFinite(value)) {
+  if (!NUMBER_IS_FINITE(value)) {
     if (value > 0) {
       return 'Infinity';
     } else {
       return '-Infinity';
     }
   }
   return value;
 }