[es6] Tail calls support.

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 188 matching lines @@
 
 // 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")    \
+  V(harmony_tailcalls, "harmony tail calls")                  \
   V(harmony_species, "harmony Symbol.species")                \
   V(harmony_object_values_entries, "harmony Object.values / Object.entries")
 
 // Features that are complete (but still behind --harmony/es-staging flag).
 #define HARMONY_STAGED(V)                                                 \
   V(harmony_regexp_lookbehind, "harmony regexp lookbehind")
 
 // Features that are shipping (turned on by default, but internal flag remains).
 #define HARMONY_SHIPPING(V)                                               \
   V(harmony_default_parameters, "harmony default parameters")             \
@@ skipping 921 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