Added Sky Mojo embedder singleton, restored network test

sky/framework/embedder.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.
+
+import "/mojo/public/dart/application.dart";
+import "dart:mojo_bindings" as bindings;
+import "dart:mojo_core" as core;
+import "dart:sky.internals" as internals;
+import "package:mojo/public/interfaces/application/service_provider.mojom.dart";
+import "package:mojo/public/interfaces/application/shell.mojom.dart";
+
+final _EmbedderImpl embedder = new _EmbedderImpl();
+
+class _EmbedderImpl {
+  final ShellProxy shell = new ShellProxy.fromHandle(
+      new core.MojoHandle(internals.takeShellProxyHandle())); 
+
+  ApplicationConnection connectToApplication(String url) {
+    var proxy = new ServiceProviderProxy.unbound();
+    var stub = new ServiceProviderStub.unbound();
+    shell.connectToApplication(url, proxy, stub);
+    return new ApplicationConnection(stub, proxy);
+  }
+
+  void connectToService(String url, bindings.Proxy proxy) {
+    var appSp = new ServiceProviderProxy.unbound();
+    shell.connectToApplication(url, appSp, null);
+    var pipe = new core.MojoMessagePipe();
+    proxy.bind(pipe.endpoints[0]);
+    appSp.connectToService(proxy.name, pipe.endpoints[1]);
+    appSp.close();
+  }
+}
+