[api] Default native data property setter to replace the setter if the property is writable.

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 850 matching lines @@
 
 DEFINE_BOOL(manual_evacuation_candidates_selection, false,
             "Test mode only flag. It allows an unit test to select evacuation "
             "candidates pages (requires --stress_compaction).")
 
 // api.cc
 DEFINE_INT(external_allocation_limit_incremental_time, 1,
            "Time spent in incremental marking steps (in ms) once the external "
            "allocation limit is reached")
 
+DEFINE_BOOL(disable_old_api_accessors, false,
+            "Disable old-style API accessors whose setters trigger through the "
+            "prototype chain")
+
 //
 // Dev shell flags
 //
 
 DEFINE_BOOL(help, false, "Print usage message, including flags, on console")
 DEFINE_BOOL(dump_counters, false, "Dump counters on exit")
 
 DEFINE_STRING(map_counters, "", "Map counters to a file")
 DEFINE_ARGS(js_arguments,
             "Pass all remaining arguments to the script. Alias for \"--\".")
@@ skipping 259 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