service_registry.dart should use the service registry handle instead of

shell handle.

R=@abarth,@tonygentilcore

packages/flutter/lib/src/services/service_registry.dart

@@ -8,7 +8,7 @@ import 'package:mojo_services/mojo/service_registry.mojom.dart';
 import 'package:mojo/core.dart' as core;
 
 ServiceRegistryProxy _initServiceRegistryProxy() {
-  core.MojoHandle serviceRegistryHandle = new core.MojoHandle(internals.takeShellProxyHandle());
+  core.MojoHandle serviceRegistryHandle = new core.MojoHandle(internals.takeServiceRegistry());
   if (!serviceRegistryHandle.isValid)
     return null;
   return new ServiceRegistryProxy.fromHandle(serviceRegistryHandle);