Expose Service Describer in Dart mojo package

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

Index: mojo/dart/packages/mojo_services/lib/mojo/gfx/composition/renderers.mojom.dart
diff --git a/mojo/dart/packages/mojo_services/lib/mojo/gfx/composition/renderers.mojom.dart b/mojo/dart/packages/mojo_services/lib/mojo/gfx/composition/renderers.mojom.dart
index 9f3f9c683ce372d4d2aeb8dca0b00a86e76c8493..457c09fadf5e89aac06bd514e80149dce6ac6609 100644
--- a/mojo/dart/packages/mojo_services/lib/mojo/gfx/composition/renderers.mojom.dart
+++ b/mojo/dart/packages/mojo_services/lib/mojo/gfx/composition/renderers.mojom.dart
@@ -199,11 +199,14 @@ const int _Renderer_getHitTesterName = 1;
 
 
 class _RendererServiceDescription 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 Renderer {
@@ -391,8 +394,13 @@ class RendererStub extends bindings.Stub {
 
   int get version => 0;
 
-  service_describer.ServiceDescription get serviceDescription =>
-    new _RendererServiceDescription();
+  static service_describer.ServiceDescription _cachedServiceDescription;
+  static service_describer.ServiceDescription get serviceDescription {
+    if (_cachedServiceDescription == null) {
+      _cachedServiceDescription = new _RendererServiceDescription();
+    }
+    return _cachedServiceDescription;
+  }
 }