Stage well-formed JSON.stringify

The proposal is currently at Stage 3 of the TC39 process.

Repository: https://github.com/tc39/proposal-well-formed-stringify

Bug: v8:7782
Change-Id: Id46054ec6873ca2d1bc8113b8c82b58b1b8427d2
Reviewed-on: https://chromium-review.googlesource.com/c/1257921Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Commit-Queue: Mathias Bynens <mathias@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56357}

src/flag-definitions.h

@@ -209,12 +209,11 @@ DEFINE_IMPLICATION(harmony_class_fields, harmony_private_fields)
 // Update bootstrapper.cc whenever adding a new feature flag.
 
 // Features that are still work in progress (behind individual flags).
-#define HARMONY_INPROGRESS_BASE(V)                                 \
-  V(harmony_do_expressions, "harmony do-expressions")              \
-  V(harmony_class_fields, "harmony fields in class literals")      \
-  V(harmony_await_optimization, "harmony await taking 1 tick")     \
-  V(harmony_regexp_sequence, "RegExp Unicode sequence properties") \
-  V(harmony_json_stringify, "Well-formed JSON.stringify")
+#define HARMONY_INPROGRESS_BASE(V)                             \
+  V(harmony_do_expressions, "harmony do-expressions")          \
+  V(harmony_class_fields, "harmony fields in class literals")  \
+  V(harmony_await_optimization, "harmony await taking 1 tick") \
+  V(harmony_regexp_sequence, "RegExp Unicode sequence properties")
 
 #ifdef V8_INTL_SUPPORT
 #define HARMONY_INPROGRESS(V)      \
@@ -231,7 +230,8 @@ DEFINE_IMPLICATION(harmony_class_fields, harmony_private_fields)
   V(harmony_private_fields, "harmony private fields in class literals")    \
   V(harmony_numeric_separator, "harmony numeric separator between digits") \
   V(harmony_string_matchall, "harmony String.prototype.matchAll")          \
-  V(harmony_static_fields, "harmony static fields in class literals")
+  V(harmony_static_fields, "harmony static fields in class literals")      \
+  V(harmony_json_stringify, "Well-formed JSON.stringify")
 
 // Features that are shipping (turned on by default, but internal flag remains).
 #define HARMONY_SHIPPING_BASE(V)                                         \