[regexp] Ship named captures

Intent to ship: goo.gl/QZ4QZ5

Bug: v8:5437
Change-Id: Icdacceefa3085f2657edd7f99c7d8f4dbbb76814
Reviewed-on: https://chromium-review.googlesource.com/727200Reviewed-by: Michael Hablich <hablich@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48721}

src/flag-definitions.h

@@ -203,7 +203,6 @@ 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_function_tostring, "harmony Function.prototype.toString")   \
-  V(harmony_regexp_named_captures, "harmony regexp named captures")     \
   V(harmony_regexp_property, "harmony Unicode regexp property classes") \
   V(harmony_restrict_constructor_return,                                \
     "harmony disallow non undefined primitive return value from class " \
@@ -230,6 +229,7 @@ DEFINE_IMPLICATION(harmony_import_meta, harmony_dynamic_import)
   V(harmony_sharedarraybuffer, "harmony sharedarraybuffer")              \
   V(harmony_regexp_dotall, "harmony regexp dotAll flag")                 \
   V(harmony_regexp_lookbehind, "harmony regexp lookbehind")              \
+  V(harmony_regexp_named_captures, "harmony regexp named captures")      \
   V(harmony_async_iteration, "harmony async iteration")                  \
   V(harmony_template_escapes,                                            \
     "harmony invalid escapes in tagged template literals")               \