Add test case for issue 7191.

tests/standalone/io/regress_7191_script.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.
+
+import 'dart:io';
+import 'dart:isolate';
+
+main() {
+  // Open a port to make the script hang.
+  var port = new ReceivePort();
+  // Start sub-process when receiving data.
+  stdin.onData = () {
+    var data = stdin.read();
+    var options = new Options();
+    Process.start(options.executable, [options.script]).then((p) {
+      p.stdout.onData = p.stdout.read;
+      p.stderr.onData = p.stderr.read;
+      stdout.close();
+      // When receiving data again, kill sub-process and exit.
+      stdin.onData = () {
+        var data = stdin.read();
+        Expect.listEquals([1], data);
+        p.kill();
+        p.onExit = port.close;
+      };
+    });
+  };
+}