cleanup patch generation to preseve comments and remove @patch

test/dart_codegen/expect/_internal/list.dart

Index: test/dart_codegen/expect/_internal/list.dart
diff --git a/test/dart_codegen/expect/_internal/list.dart b/test/dart_codegen/expect/_internal/list.dart
index f5f364f8b6ee8c8a35966709b7c913cb403f0e0c..1d0dd283ac7e013b02f6d2fb915a76714f136de8 100644
--- a/test/dart_codegen/expect/_internal/list.dart
+++ b/test/dart_codegen/expect/_internal/list.dart
@@ -178,7 +178,7 @@ abstract class NonGrowableListError {
   static UnsupportedError remove() =>
       new UnsupportedError("Cannot remove from non-growable List");
 }
-@patch List makeListFixedLength(List growableList) {
+List makeListFixedLength(List growableList) {
   JSArray.markFixedList(growableList);
   return growableList;
 }