Change analysis server protocol to omit empty lists when optional.

pkg/analysis_server/lib/src/edit/edit_domain.dart

Index: pkg/analysis_server/lib/src/edit/edit_domain.dart
diff --git a/pkg/analysis_server/lib/src/edit/edit_domain.dart b/pkg/analysis_server/lib/src/edit/edit_domain.dart
index 2507981e742151e06e7914102034a36c88097531..99c55211f7dad033e7cc6e4ac2d6e5c75a490d15 100644
--- a/pkg/analysis_server/lib/src/edit/edit_domain.dart
+++ b/pkg/analysis_server/lib/src/edit/edit_domain.dart
@@ -90,7 +90,8 @@ class EditDomainHandler implements RequestHandler {
       }
     }
     // respond
-    return new EditGetAvailableRefactoringsResult(kinds).toResponse(request.id);
+    return new EditGetAvailableRefactoringsResult(kinds: kinds).toResponse(
+        request.id);
   }
 
   Response getFixes(Request request) {