Add top-level driver and abstract plugin superclass

pkg/analyzer_plugin/lib/starter.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 'dart:isolate';
+
+import 'package:analyzer_plugin/plugin/plugin.dart';
+import 'package:analyzer_plugin/src/driver.dart';
+
+/**
+ * An object that can be used to start an analysis server plugin. This class
+ * exists so that clients can configure a plugin before starting it.
+ *
+ * Clients may not extend, implement or mix-in this class.
+ */
+abstract class ServerPluginStarter {
+  /**
+   * Create a starter that can be used to start the given [plugin].
+   */
+  factory ServerPluginStarter(ServerPlugin plugin) => new Driver(plugin);
+
+  /**
+   * Establish the channel used to communicate with the server and start the
+   * plugin.
+   */
+  void start(SendPort sendPort);
+}