Example of deadlock in test_runner.dart on process crash

tools/testing/dart/test_runner.dart

Index: tools/testing/dart/test_runner.dart
diff --git a/tools/testing/dart/test_runner.dart b/tools/testing/dart/test_runner.dart
index d3c97e120ff8a83775c6a784639b05e0695b601d..15c4c95e718dbd51cb210960fc2d76c47574a4bb 100644
--- a/tools/testing/dart/test_runner.dart
+++ b/tools/testing/dart/test_runner.dart
@@ -671,6 +671,7 @@ class BatchRunnerProcess {
   }
 
   int _reportResult(String output) {
+    print ("_stdoutDrained: ${_currentTest.displayName}");
     _stdoutDrained = true;
     // output = '>>> TEST {PASS, FAIL, OK, CRASH, FAIL, TIMEOUT}'
     var outcome = output.split(" ")[2];
@@ -684,6 +685,7 @@ class BatchRunnerProcess {
   }
 
   void _stderrDone() {
+    print ("_stdoutDrained: ${_currentTest.displayName}");
     _stderrDrained = true;
     // Move on when both stdout and stderr has been drained.
     if (_stdoutDrained) _testCompleted();
@@ -732,6 +734,9 @@ class BatchRunnerProcess {
   void _exitHandler(exitCode) {
     if (_timer != null) _timer.cancel();
     _process.close();
+    if (!(_stdoutDrained && stderrDrained)) {
+      print("*** POTENTIAL DEADLOCK on process restart");
+    }
     _startProcess(() {
       _reportResult(">>> TEST CRASH");
     });