Avoid exceptions when analyzing truncated test output.

tools/testing/dart/test_runner.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * Classes and methods for executing tests.
  *
  * This module includes:
  * - Managing parallel execution of tests, including timeout checks.
  * - Evaluating the output of each test as pass/fail/crash/timeout.
@@ skipping 1446 matching lines @@
         field.write(c);
       }
       result.add(field.toString());
       return result;
     }
 
     for (String line in decodeUtf8(super.stderr).split("\n")) {
       if (line.length == 0) continue;
       List<String> fields = splitMachineError(line);
       // We only consider errors/warnings for files of interest.
-      if (fields.length > FILENAME) {
+      if (fields.length > FORMATTED_ERROR) {
         if (fields[ERROR_LEVEL] == 'ERROR') {
           outErrors.add(fields[FORMATTED_ERROR]);
         } else if (fields[ERROR_LEVEL] == 'WARNING') {
           outWarnings.add(fields[FORMATTED_ERROR]);
         }
         // OK to Skip error output that doesn't match the machine format
       }
     }
   }
 }
@@ skipping 1456 matching lines @@
     }
   }
 
   void eventAllTestsDone() {
     for (var listener in _eventListener) {
       listener.allDone();
     }
     _allDone();
   }
 }