Expose Service Describer in Dart mojo package

mojo/dart/packages/mojo_services/lib/mojo/media/media_factory.mojom.dart

Index: mojo/dart/packages/mojo_services/lib/mojo/media/media_factory.mojom.dart
diff --git a/mojo/dart/packages/mojo_services/lib/mojo/media/media_factory.mojom.dart b/mojo/dart/packages/mojo_services/lib/mojo/media/media_factory.mojom.dart
index ea2e76225a5a34a60eb18638273b058f28634170..ce5554f6f47669b5afffb71afea41981f04c522e 100644
--- a/mojo/dart/packages/mojo_services/lib/mojo/media/media_factory.mojom.dart
+++ b/mojo/dart/packages/mojo_services/lib/mojo/media/media_factory.mojom.dart
@@ -327,11 +327,14 @@ const int _MediaFactory_createSinkName = 2;
 
 
 class _MediaFactoryServiceDescription 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 MediaFactory {
@@ -537,7 +540,7 @@ class MediaFactoryStub extends bindings.Stub {
 
   int get version => 0;
 
-  service_describer.ServiceDescription get serviceDescription =>
+  static service_describer.ServiceDescription get serviceDescription =>
     new _MediaFactoryServiceDescription();
 }