Add ES2015 RegExp full subclassing semantics behind a flag

src/bootstrapper.cc

Index: src/bootstrapper.cc
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index 8eeae17aa5004e8861f410207256adf4e1461b4e..d0845383b0eadcdda7d3586508ff77a15b0d852a 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -2360,6 +2360,7 @@ EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_regexps)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_unicode_regexps)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_do_expressions)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_iterator_close)
+EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_regexp_exec)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_regexp_lookbehind)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_regexp_property)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_function_name)
@@ -2938,6 +2939,8 @@ bool Genesis::InstallExperimentalNatives() {
   static const char* harmony_simd_natives[] = {"native harmony-simd.js",
                                                nullptr};
   static const char* harmony_do_expressions_natives[] = {nullptr};
+  static const char* harmony_regexp_exec_natives[] = {
+      "native harmony-regexp-exec.js", nullptr};
   static const char* harmony_regexp_subclass_natives[] = {nullptr};
   static const char* harmony_regexp_lookbehind_natives[] = {nullptr};
   static const char* harmony_instanceof_natives[] = {nullptr};