Add an incremental reloader example and a utility tool to trigger a reload by

pkg/front_end/tool/vm/reload.dart

+// Copyright (c) 2017, 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 'package:front_end/src/vm/reload.dart';
+
+/// Connects to an existing VM's service protocol and issues a hot-reload
+/// request. The VM must have been launched with `--observe` to enable the
+/// service protocol.
+///
+// TODO(sigmund): provide flags to configure the vm-service port.
+main(List<String> args) async {
+  if (args.length == 0) {
+    print('usage: reload <entry-uri>');
+    return;
+  }
+
+  var reloader = new VmReloader();
+  await reloader.reload(Uri.base.resolve(args.first));
+  await reloader.disconnect();
+}