[esnext] implement frontend changes for async/await proposal

src/bootstrapper.cc

Index: src/bootstrapper.cc
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index 9af851f710d25c5476ab924bbbe8850adb9986cb..bd228352721af48b312261da81d55c6c07bcb758 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -2450,6 +2450,7 @@ EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_instanceof)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_restrictive_declarations)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_exponentiation_operator)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_string_padding)
+EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_async_await)
 
 void InstallPublicSymbol(Factory* factory, Handle<Context> native_context,
                          const char* name, Handle<Symbol> value) {
@@ -3018,6 +3019,7 @@ bool Genesis::InstallExperimentalNatives() {
   static const char* harmony_exponentiation_operator_natives[] = {nullptr};
   static const char* harmony_string_padding_natives[] = {
       "native harmony-string-padding.js", nullptr};
+  static const char* harmony_async_await_natives[] = {nullptr};
 
   for (int i = ExperimentalNatives::GetDebuggerCount();
        i < ExperimentalNatives::GetBuiltinsCount(); i++) {