Fix Error.prototype.toString to be ES5 conform.

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 1069 matching lines @@
  */
 ErrorMirror.prototype.message = function() {
   return this.value_.message;
 };
 
 
 ErrorMirror.prototype.toText = function() {
   // Use the same text representation as in messages.js.
   var text;
   try {
-    str = %_CallFunction(this.value_, builtins.errorToString);
+    str = %_CallFunction(this.value_, builtins.ErrorToString);
   } catch (e) {
     str = '#<Error>';
   }
   return str;
 }
 
 
 /**
  * Base mirror object for properties.
  * @param {ObjectMirror} mirror The mirror object having this property
@@ skipping 1319 matching lines @@
   }
   if (!NUMBER_IS_FINITE(value)) {
     if (value > 0) {
       return 'Infinity';
     } else {
       return '-Infinity';
     }
   }
   return value;
 }