Fix issue 420: accept truncated log files.

test/mjsunit/tools/logreader.js

 // Copyright 2009 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 62 matching lines @@
 
 
 (function testExpandBackRef() {
   var reader = new devtools.profiler.LogReader({});
 
   assertEquals('aaaaaaaa', reader.expandBackRef_('aaaaaaaa'));
   assertEquals('aaaaaaaa', reader.expandBackRef_('#1'));
   assertEquals('bbbbaaaa', reader.expandBackRef_('bbbb#2:4'));
   assertEquals('"#1:1"', reader.expandBackRef_('"#1:1"'));
 })();
+
+
+// See http://code.google.com/p/v8/issues/detail?id=420
+(function testReadingTruncatedLog() {
+  // Having an incorrect event in the middle of a log should throw an exception.
+  var reader1 = new devtools.profiler.LogReader({});
+  assertThrows(function() {
+    reader1.processLogChunk('alias,a,b\nxxxx\nalias,c,d\n');
+  });
+
+  // But having it as the last record should not.
+  var reader2 = new devtools.profiler.LogReader({});
+  assertDoesNotThrow(function() {
+    reader2.processLogChunk('alias,a,b\nalias,c,d\nxxxx');
+  });
+})();