Enable --harmony-trailing-commas

src/flag-definitions.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file defines all of the flags.  It is separated into different section,
 // for Debug, Release, Logging and Profiling, etc.  To add a new flag, find the
 // correct section, and use one of the DEFINE_ macros, without a trailing ';'.
 //
 // This include does not have a guard, because it is a template-style include,
 // which can be included multiple times in different modes.  It expects to have
@@ skipping 193 matching lines @@
   V(harmony_regexp_property, "harmony unicode regexp property classes")  \
   V(harmony_class_fields, "harmony public fields in class literals")     \
   V(harmony_async_iteration, "harmony async iteration")
 
 // Features that are complete (but still behind --harmony/es-staging flag).
 #define HARMONY_STAGED(V)                                   \
   V(harmony_regexp_lookbehind, "harmony regexp lookbehind") \
   V(harmony_restrictive_generators,                         \
     "harmony restrictions on generator declarations")       \
   V(harmony_tailcalls, "harmony tail calls")                \
-  V(harmony_trailing_commas,                                \
-    "harmony trailing commas in function parameter lists")  \
   V(harmony_object_rest_spread, "harmony object rest spread properties")
 
 // Features that are shipping (turned on by default, but internal flag remains).
-#define HARMONY_SHIPPING_BASE(V)
+#define HARMONY_SHIPPING_BASE(V) \
+  V(harmony_trailing_commas,     \
+    "harmony trailing commas in function parameter lists")
 
 #ifdef V8_I18N_SUPPORT
 #define HARMONY_SHIPPING(V)                                        \
   HARMONY_SHIPPING_BASE(V)                                         \
   V(datetime_format_to_parts, "Intl.DateTimeFormat.formatToParts") \
   V(icu_case_mapping, "case mapping with ICU rather than Unibrow")
 #else
 #define HARMONY_SHIPPING(V) HARMONY_SHIPPING_BASE(V)
 #endif
 
@@ skipping 1076 matching lines @@
 #undef DEFINE_ALIAS_FLOAT
 #undef DEFINE_ALIAS_ARGS
 
 #undef FLAG_MODE_DECLARE
 #undef FLAG_MODE_DEFINE
 #undef FLAG_MODE_DEFINE_DEFAULTS
 #undef FLAG_MODE_META
 #undef FLAG_MODE_DEFINE_IMPLICATIONS
 
 #undef COMMA