Add Observatory mojo_shell hearbeat test

mojo/dart/embedder/vmservice/server.dart

 // Copyright 2015 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 dart_controller_service_isolate;
 
 class WebSocketClient extends Client {
   static const int PARSE_ERROR_CODE = 4000;
   static const int BINARY_MESSAGE_ERROR_CODE = 4001;
   static const int NOT_MAP_ERROR_CODE = 4002;
@@ skipping 133 matching lines @@
       assert(resource != null);
     }
     if (resource != null) {
       // Serving up a static resource (e.g. .css, .html, .png).
       request.response.headers.contentType =
           ContentType.parse(resource.mimeType);
       request.response.add(resource.data);
       request.response.close();
       return;
     }
-    var message = new Message.fromUri(this, request.uri);
     var client = new HttpRequestClient(request, _service);
+    var message = new Message.fromUri(client, request.uri);
     client.onMessage(null, message);
   }
 
   Future startup() {
     if (_server != null) {
       // Already running.
       return new Future.value(this);
     }
 
     // Startup HTTP server.
@@ skipping 50 matching lines @@
       print('Could not shutdown Observatory HTTP server:\n$e\n$st\n');
       _notifyServerState("", 0);
       return this;
     });
   }
 
 }
 
 _notifyServerState(String ip, int port)
     native "ServiceIsolate_NotifyServerState";