Add some temporary code to work around an error in test scripts, to fix buildbots.

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 712 matching lines @@
     _timer = new Timer(testCase.timeout * 1000, _timeoutHandler);
     var line = _createArgumentsLine(testCase.batchTestArguments);
     _process.stdin.write(line.charCodes());
   }
 
   String _createArgumentsLine(List<String> arguments) {
     return Strings.join(arguments, ' ').concat('\n');
   }
 
   void _testCompleted() {
+    // TODO(3286): Remove this temporary code used to diagnose problem.
+    if (!_stdoutDrained || !_stderrDrained) {
+      print("Warning: Batch Test Runner problem:\n"
+          "  _stdoutDrained: $_stdoutDrained, _stderrDrained: $_stderrDrained");
+    }
     var test = _currentTest;
     _currentTest = null;
     test.completed();
   }
 
   int _reportResult(String output) {
     _stdoutDrained = true;
     // output = '>>> TEST {PASS, FAIL, OK, CRASH, FAIL, TIMEOUT}'
     var outcome = output.split(" ")[2];
     var exitCode = 0;
     if (outcome == "CRASH") exitCode = -10;
     if (outcome == "FAIL" || outcome == "TIMEOUT") exitCode = 1;
-    new TestOutput.fromCase(_currentTest, exitCode, (outcome == "TIMEOUT"),
-                            _testStdout, _testStderr,
-                            new Date.now().difference(_startTime));
+    // TODO(3286): Remove this temporary code used to diagnose problem.
+    if (_currentTest == null) {
+      print("Warning: Batch Test Runner problem:\n"
+            "    _currentTest is null\n"
+            "    Stdout:");
+      for (var line in _testStdout) {
+        print(line);
+      }
+      print("    Stderr:");
+      for (var line in _testStderr) {
+        print(line);
+      }
+    } else {
+      new TestOutput.fromCase(_currentTest, exitCode, (outcome == "TIMEOUT"),
+                              _testStdout, _testStderr,
+                              new Date.now().difference(_startTime));
+    }
     // Move on when both stdout and stderr has been drained. If the test
     // crashed, we restarted the process and therefore do not attempt to
     // drain stderr.
     if (_stderrDrained || (_currentTest.output.hasCrashed)) _testCompleted();
   }
 
   void _stderrDone() {
     _stderrDrained = true;
     // Move on when both stdout and stderr has been drained.
     if (_stdoutDrained) _testCompleted();
@@ skipping 378 matching lines @@
         // the developer doesn't waste his or her time trying to fix a bunch of
         // tests that appear to be broken but were actually just flakes that
         // didn't get retried because there had already been one failure.
         bool allowRetry = _MAX_FAILED_NO_RETRY > _progress.numFailedTests;
         new RunningProcess(test, allowRetry, this).start();
       }
       _numProcesses++;
     }
   }
 }