Expose Service Describer in Dart mojo package

mojo/dart/packages/_mojo_for_test_only/lib/sample/sample_service.mojom.dart

Index: mojo/dart/packages/_mojo_for_test_only/lib/sample/sample_service.mojom.dart
diff --git a/mojo/dart/packages/_mojo_for_test_only/lib/sample/sample_service.mojom.dart b/mojo/dart/packages/_mojo_for_test_only/lib/sample/sample_service.mojom.dart
index eaee0d99975ab47cc0c09656b44d35f979790a64..8baadc38ea1c4c32486371ae3ba60dcdf23405db 100644
--- a/mojo/dart/packages/_mojo_for_test_only/lib/sample/sample_service.mojom.dart
+++ b/mojo/dart/packages/_mojo_for_test_only/lib/sample/sample_service.mojom.dart
@@ -2291,13 +2291,13 @@ mojom_types.MojomInterface _sampleServiceService() {
 
 class _ServiceServiceDescription implements service_describer.ServiceDescription {
   dynamic getTopLevelInterface([Function responseFactory]) =>
-      _sampleServiceService();
+    responseFactory(_sampleServiceService());
 
   dynamic getTypeDefinition(String typeKey, [Function responseFactory]) =>
-      getAllMojomTypeDefinitions()[typeKey];
+    responseFactory(getAllMojomTypeDefinitions()[typeKey]);
 
   dynamic getAllTypeDefinitions([Function responseFactory]) =>
-      getAllMojomTypeDefinitions();
+    responseFactory(getAllMojomTypeDefinitions());
 }
 
 abstract class Service {
@@ -2528,8 +2528,13 @@ class ServiceStub extends bindings.Stub {
 
   int get version => 0;
 
-  service_describer.ServiceDescription get serviceDescription =>
-    new _ServiceServiceDescription();
+  static service_describer.ServiceDescription _cachedServiceDescription;
+  static service_describer.ServiceDescription get serviceDescription {
+    if (_cachedServiceDescription == null) {
+      _cachedServiceDescription = new _ServiceServiceDescription();
+    }
+    return _cachedServiceDescription;
+  }
 }
 
 const int _Port_postMessageName = 0;
@@ -2551,13 +2556,13 @@ mojom_types.MojomInterface _sampleServicePort() {
 
 class _PortServiceDescription implements service_describer.ServiceDescription {
   dynamic getTopLevelInterface([Function responseFactory]) =>
-      _sampleServicePort();
+    responseFactory(_sampleServicePort());
 
   dynamic getTypeDefinition(String typeKey, [Function responseFactory]) =>
-      getAllMojomTypeDefinitions()[typeKey];
+    responseFactory(getAllMojomTypeDefinitions()[typeKey]);
 
   dynamic getAllTypeDefinitions([Function responseFactory]) =>
-      getAllMojomTypeDefinitions();
+    responseFactory(getAllMojomTypeDefinitions());
 }
 
 abstract class Port {
@@ -2729,8 +2734,13 @@ class PortStub extends bindings.Stub {
 
   int get version => 0;
 
-  service_describer.ServiceDescription get serviceDescription =>
-    new _PortServiceDescription();
+  static service_describer.ServiceDescription _cachedServiceDescription;
+  static service_describer.ServiceDescription get serviceDescription {
+    if (_cachedServiceDescription == null) {
+      _cachedServiceDescription = new _PortServiceDescription();
+    }
+    return _cachedServiceDescription;
+  }
 }