Avoid callbacks to user code during error formatting in a couple of

test/mjsunit/mirror-error.js

 // Copyright 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 58 matching lines @@
     for (var i in fromJSON.properties) {
       var p = fromJSON.properties[i];
       print(p.name);
       if (p.name == 'message') {
         assertEquals(e.message, refs.lookup(p.ref).value);
         found_message = true;
       }
     }
     assertTrue(found_message, 'Property message not found');
   }
-  
+
   // Check the formatted text (regress 1231579).
   assertEquals(fromJSON.text, e.toString(), 'toString');
 }
 
 
 // Test Date values.
 testErrorMirror(new Error());
 testErrorMirror(new Error('This does not work'));
 testErrorMirror(new Error(123+456));
 testErrorMirror(new EvalError('EvalError'));
 testErrorMirror(new RangeError('RangeError'));
 testErrorMirror(new ReferenceError('ReferenceError'));
 testErrorMirror(new SyntaxError('SyntaxError'));
 testErrorMirror(new TypeError('TypeError'));
 testErrorMirror(new URIError('URIError'));