Expose Service Describer in Dart mojo package

mojo/dart/packages/mojo_services/lib/icu_data/icu_data.mojom.dart

Index: mojo/dart/packages/mojo_services/lib/icu_data/icu_data.mojom.dart
diff --git a/mojo/dart/packages/mojo_services/lib/icu_data/icu_data.mojom.dart b/mojo/dart/packages/mojo_services/lib/icu_data/icu_data.mojom.dart
index 9062ae40903972c59adf7bda3e726e8b708c8e15..2b5ea25bc707f212174bcb99065949376ad2ea6e 100644
--- a/mojo/dart/packages/mojo_services/lib/icu_data/icu_data.mojom.dart
+++ b/mojo/dart/packages/mojo_services/lib/icu_data/icu_data.mojom.dart
@@ -165,11 +165,14 @@ const int _IcuData_mapName = 0;
 
 
 class _IcuDataServiceDescription 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 IcuData {
@@ -382,8 +385,13 @@ class IcuDataStub extends bindings.Stub {
 
   int get version => 0;
 
-  service_describer.ServiceDescription get serviceDescription =>
-    new _IcuDataServiceDescription();
+  static service_describer.ServiceDescription _cachedServiceDescription;
+  static service_describer.ServiceDescription get serviceDescription {
+    if (_cachedServiceDescription == null) {
+      _cachedServiceDescription = new _IcuDataServiceDescription();
+    }
+    return _cachedServiceDescription;
+  }
 }