Stage RegExp subclassing

src/flag-definitions.h

Index: src/flag-definitions.h
diff --git a/src/flag-definitions.h b/src/flag-definitions.h
index c44e15dcf12244cae65dfdb4c6f722081bcaf84e..8a9436e6b26aa634096790ea7d51ad68eff4c126 100644
--- a/src/flag-definitions.h
+++ b/src/flag-definitions.h
@@ -205,14 +205,14 @@ DEFINE_IMPLICATION(es_staging, move_object_start)
   V(harmony_sharedarraybuffer, "harmony sharedarraybuffer")   \
   V(harmony_simd, "harmony simd")                             \
   V(harmony_do_expressions, "harmony do-expressions")         \
-  V(harmony_regexp_subclass, "harmony regexp subclassing")    \
   V(harmony_tailcalls, "harmony tail calls")                  \
   V(harmony_species, "harmony Symbol.species")                \
   V(harmony_object_values_entries, "harmony Object.values / Object.entries")
 
 // Features that are complete (but still behind --harmony/es-staging flag).
-#define HARMONY_STAGED(V)                                                 \
-  V(harmony_regexp_lookbehind, "harmony regexp lookbehind")
+#define HARMONY_STAGED(V)                                   \
+  V(harmony_regexp_lookbehind, "harmony regexp lookbehind") \
+  V(harmony_regexp_subclass, "harmony regexp subclassing")
 
 // Features that are shipping (turned on by default, but internal flag remains).
 #define HARMONY_SHIPPING(V)                                               \