Expose Service Describer in Dart mojo package

mojo/dart/packages/mojo_services/lib/mojo/gfx/composition/compositor.mojom.dart

Index: mojo/dart/packages/mojo_services/lib/mojo/gfx/composition/compositor.mojom.dart
diff --git a/mojo/dart/packages/mojo_services/lib/mojo/gfx/composition/compositor.mojom.dart b/mojo/dart/packages/mojo_services/lib/mojo/gfx/composition/compositor.mojom.dart
index 7428c77ca820bb9a1dfd1351000bd4fb6fd4975a..9fc5c3c41ed927d2138cb40fd308561ca4b4455b 100644
--- a/mojo/dart/packages/mojo_services/lib/mojo/gfx/composition/compositor.mojom.dart
+++ b/mojo/dart/packages/mojo_services/lib/mojo/gfx/composition/compositor.mojom.dart
@@ -285,11 +285,14 @@ const int _Compositor_createRendererName = 1;
 
 
 class _CompositorServiceDescription implements service_describer.ServiceDescription {
-  dynamic getTopLevelInterface([Function responseFactory]) => null;
+  dynamic getTopLevelInterface([Function responseFactory]) =>
+      responseFactory(null);
 
-  dynamic getTypeDefinition(String typeKey, [Function responseFactory]) => null;
+  dynamic getTypeDefinition(String typeKey, [Function responseFactory]) =>
+      responseFactory(null);
 
-  dynamic getAllTypeDefinitions([Function responseFactory]) => null;
+  dynamic getAllTypeDefinitions([Function responseFactory]) =>
+      responseFactory(null);
 }
 
 abstract class Compositor {
@@ -520,7 +523,7 @@ class CompositorStub extends bindings.Stub {
 
   int get version => 0;
 
-  service_describer.ServiceDescription get serviceDescription =>
+  static service_describer.ServiceDescription get serviceDescription =>
     new _CompositorServiceDescription();
 }