Add a --harmony-species flag, defining @@species on constructors

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 180 matching lines @@
 
 DEFINE_BOOL(promise_extra, true, "additional V8 Promise functions")
 // Removing extra Promise functions is staged
 DEFINE_NEG_IMPLICATION(harmony, promise_extra)
 
 // Activate on ClusterFuzz.
 DEFINE_IMPLICATION(es_staging, harmony_regexp_lookbehind)
 DEFINE_IMPLICATION(es_staging, move_object_start)
 
 // Features that are still work in progress (behind individual flags).
-#define HARMONY_INPROGRESS(V)                                         \
-  V(harmony_modules, "harmony modules")                               \
-  V(harmony_unicode_regexps, "harmony unicode regexps")               \
-  V(harmony_function_name, "harmony Function name inference")         \
-  V(harmony_sharedarraybuffer, "harmony sharedarraybuffer")           \
-  V(harmony_simd, "harmony simd")                                     \
-  V(harmony_do_expressions, "harmony do-expressions")                 \
-  V(harmony_regexp_subclass, "harmony regexp subclassing")
+#define HARMONY_INPROGRESS(V)                                 \
+  V(harmony_modules, "harmony modules")                       \
+  V(harmony_unicode_regexps, "harmony unicode regexps")       \
+  V(harmony_function_name, "harmony Function name inference") \
+  V(harmony_sharedarraybuffer, "harmony sharedarraybuffer")   \
+  V(harmony_simd, "harmony simd")                             \
+  V(harmony_do_expressions, "harmony do-expressions")         \
+  V(harmony_regexp_subclass, "harmony regexp subclassing")    \
+  V(harmony_species, "harmony Symbol.species")
 
 // Features that are complete (but still behind --harmony/es-staging flag).
 #define HARMONY_STAGED(V)                                                 \
   V(harmony_destructuring_assignment, "harmony destructuring assignment") \
   V(harmony_proxies, "harmony proxies")                                   \
   V(harmony_reflect, "harmony Reflect API")                               \
   V(harmony_sloppy, "harmony features in sloppy mode")                    \
   V(harmony_sloppy_let, "harmony let in sloppy mode")                     \
   V(harmony_sloppy_function, "harmony sloppy function block scoping")     \
   V(harmony_regexp_lookbehind, "harmony regexp lookbehind")
@@ skipping 915 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