Allow trailing commas in function parameter lists

src/bootstrapper.cc

Index: src/bootstrapper.cc
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index 199ac4125e6eb202e22bb2f9a88ea91452d99fcb..b0bc0dce6d1950393e6edff5d1a6666252dce59a 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -2704,6 +2704,7 @@ EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(icu_case_mapping)
 #endif
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_async_await)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_restrictive_generators)
+EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_trailing_commas_in_parameters)
 
 void InstallPublicSymbol(Factory* factory, Handle<Context> native_context,
                          const char* name, Handle<Symbol> value) {
@@ -3307,6 +3308,8 @@ bool Genesis::InstallExperimentalNatives() {
   static const char* harmony_async_await_natives[] = {
       "native harmony-async-await.js", nullptr};
   static const char* harmony_restrictive_generators_natives[] = {nullptr};
+  static const char* harmony_trailing_commas_in_parameters_natives[] = {
+      nullptr};
 
   for (int i = ExperimentalNatives::GetDebuggerCount();
        i < ExperimentalNatives::GetBuiltinsCount(); i++) {