Make Sky embedder.connection deal with null handles

mojo/public/dart/src/application_connection.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 core.Listener ServiceFactory(core.MojoMessagePipeEndpoint endpoint);
 typedef void FallbackServiceFactory(String interfaceName,
     core.MojoMessagePipeEndpoint endpoint);
 
@@ skipping 56 matching lines @@
   ApplicationConnection(ServiceProviderStub stub, ServiceProviderProxy proxy)
       : remoteServiceProvider = proxy {
     if (stub != null) _localServiceProvider =
         new LocalServiceProvider(this, stub);
   }
 
   bindings.Proxy requestService(bindings.Proxy proxy) {
     assert(!proxy.isBound &&
         (remoteServiceProvider != null) &&
         remoteServiceProvider.isBound);
-    var applicationPipe = new core.MojoMessagePipe();
-    var proxyEndpoint = applicationPipe.endpoints[0];
-    var applicationEndpoint = applicationPipe.endpoints[1];
-    proxy.bind(proxyEndpoint);
-    remoteServiceProvider.connectToService(proxy.name, applicationEndpoint);
+    var pipe = new core.MojoMessagePipe();
+    proxy.bind(pipe.endpoints[0]);
+    remoteServiceProvider.connectToService(proxy.name, pipe.endpoints[1]);
     return proxy;
   }
 
   void provideService(String interfaceName, ServiceFactory factory) {
     assert(_localServiceProvider != null);
     _nameToServiceFactory[interfaceName] = factory;
   }
 
   void listen() {
     if (_localServiceProvider != null) _localServiceProvider.listen();
   }
 
   void close({bool nodefer: false}) {
     if (remoteServiceProvider != null) {
       remoteServiceProvider.close();
       remoteServiceProvider = null;
     }
     if (_localServiceProvider != null) {
       _localServiceProvider.close(nodefer: nodefer);
       _localServiceProvider = null;
     }
 
   }
 }