Dart: Adds a content handler and a test.

services/dart/lib/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 application;
+
+typedef bindings.Interface InterfaceFactory(
+    core.MojoMessagePipeEndpoint endpoint);
+
+class ServiceProvider implements service_provider.ServiceProviderInterface {
+  InterfaceFactory _interfaceFactory;
+
+  ServiceProvider(this._interfaceFactory);
+
+  connectToService(String interfaceName, core.MojoMessagePipeEndpoint pipe) {
+    var interfaceImpl = _interfaceFactory(pipe);
+    interfaceImpl.listen();
+  }
+}