[class] stage --harmony-private-methods

Bug: v8:8330
Change-Id: I958f9db0a4f768637ca50b2b19788793236afadf
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1854014Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Joyee Cheung <joyee@igalia.com>
Cr-Commit-Position: refs/heads/master@{#64228}

src/flags/flag-definitions.h

@@ -204,7 +204,6 @@ DEFINE_IMPLICATION(harmony_import_meta, harmony_dynamic_import)
 
 // Features that are still work in progress (behind individual flags).
 #define HARMONY_INPROGRESS_BASE(V)                                        \
-  V(harmony_private_methods, "harmony private methods in class literals") \
   V(harmony_regexp_sequence, "RegExp Unicode sequence properties")        \
   V(harmony_weak_refs, "harmony weak references")                         \
   V(harmony_regexp_match_indices, "harmony regexp match indices")         \
@@ -219,7 +218,8 @@ DEFINE_IMPLICATION(harmony_import_meta, harmony_dynamic_import)
 // Features that are complete (but still behind --harmony/es-staging flag).
 #define HARMONY_STAGED_BASE(V)                                     \
   V(harmony_optional_chaining, "harmony optional chaining syntax") \
-  V(harmony_nullish, "harmony nullish operator")
+  V(harmony_nullish, "harmony nullish operator")                   \
+  V(harmony_private_methods, "harmony private methods in class literals")
 
 #ifdef V8_INTL_SUPPORT
 #define HARMONY_STAGED(V)                                           \