Fix issue 420: accept truncated log files.

test/mjsunit/mjsunit.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 161 matching lines @@
 
 function assertInstanceof(obj, type) {
   if (!(obj instanceof type)) {
     assertTrue(false, "Object <" + obj + "> is not an instance of <" + type + ">");
   }
 }
 
 
 function assertDoesNotThrow(code) {
   try {
-    eval(code);
+    if (typeof code == 'function') {
+      code();
+    } else {
+      eval(code);
+    }
   } catch (e) {
-    assertTrue(false, "threw an exception");
+    assertTrue(false, "threw an exception: " + (e.message || e));
   }
 }
 
 
 function assertUnreachable(name_opt) {
   // Fix this when we ditch the old test runner.
   var message = "Fail" + "ure: unreachable"
   if (name_opt) {
     message += " - " + name_opt;
   }
   throw new MjsUnitAssertionError(message);
 }