Dart: Adds a content handler and a test.

mojo/public/dart/src/service_provider.dart

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+part of bindings;
+
+typedef Interface InterfaceFactory(core.MojoMessagePipeEndpoint endpoint);
+
+class ServiceProvider extends service_provider.ServiceProviderInterface {
+  InterfaceFactory _interfaceFactory;
+  List<Interface> _interfaces;
+
+  ServiceProvider(core.MojoMessagePipeEndpoint endpoint,
+                  InterfaceFactory interfaceFactory) :
+      _interfaceFactory = interfaceFactory,
+      _interfaces = [],
+      super(endpoint);
+
+  connectToService(String interfaceName, core.MojoHandle pipe) {
+    var endpoint = new core.MojoMessagePipeEndpoint(pipe);
+    var interfaceImpl = _interfaceFactory(endpoint);
+    interfaceImpl.listen();
+    _interfaces.add(interfaceImpl);
+  }
+
+  void close() {
+    _interfaces.forEach((i) => i.close());
+    super.close();
+  }
+}