Stage Array.prototype.{flat,flatMap}

Proposal repo: https://tc39.github.io/proposal-flatMap/

Bug: v8:7220
Change-Id: I79022fe26c609225dce21c0b45e8bedff12cc7b5
Reviewed-on: https://chromium-review.googlesource.com/1076427Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Commit-Queue: Mathias Bynens <mathias@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53412}

src/flag-definitions.h

@@ -208,11 +208,10 @@ 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_static_fields, "harmony static fields in class literals") \
-  V(harmony_array_flat, "harmony Array.prototype.{flat,flatMap}")
+#define HARMONY_INPROGRESS_BASE(V)                            \
+  V(harmony_do_expressions, "harmony do-expressions")         \
+  V(harmony_class_fields, "harmony fields in class literals") \
+  V(harmony_static_fields, "harmony static fields in class literals")
 
 #ifdef V8_INTL_SUPPORT
 #define HARMONY_INPROGRESS(V) \
@@ -227,7 +226,8 @@ DEFINE_IMPLICATION(harmony_class_fields, harmony_private_fields)
   V(harmony_public_fields, "harmony public fields in class literals")      \
   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_string_matchall, "harmony String.prototype.matchAll")          \
+  V(harmony_array_flat, "harmony Array.prototype.{flat,flatMap}")
 
 // Features that are shipping (turned on by default, but internal flag remains).
 #define HARMONY_SHIPPING(V)                                                   \