Dart: Adds a content handler and a test.

services/dart/test/echo.dart

+#!mojo mojo:dart_content_handler
+
+// 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.
+
+import 'dart:async';
+import 'dart:mojo_application';
+import 'dart:mojo_bindings';
+import 'dart:mojo_core';
+
+import 'package:services/dart/test/echo_service.mojom.dart';
+
+// TODO(zra): Interface implementations that delegate to another implementation
+// will all look the same, more or less. Maybe we should generate them?
+class EchoServiceImpl extends EchoServiceInterface {
+  EchoServiceInterface _delegate;
+
+  EchoServiceImpl(this._delegate, MojoMessagePipeEndpoint endpoint) :
+      super(endpoint);
+
+  echoString(String value) => _delegate.echoString(value);
+}
+
+class EchoApplication extends Application implements EchoServiceInterface {
+  EchoApplication(MojoMessagePipeEndpoint endpoint) : super(endpoint);
+
+  EchoApplication.fromHandle(MojoHandle handle) : super.fromHandle(handle);
+
+  Function interfaceFactoryClosure() {
+    return (endpoint) => new EchoServiceImpl(this, endpoint);
+  }
+
+  echoString(String value) {
+    var response = new EchoServiceEchoStringResponseParams();
+    if (value == 'quit') {
+      close();
+    }
+    response.value = value;
+    return new Future.value(response);
+  }
+}
+
+main(List args) {
+  MojoHandle shellHandle = new MojoHandle(args[0]);
+  String url = args[1];
+  var echoApplication = new EchoApplication.fromHandle(shellHandle);
+  echoApplication.listen();
+}