[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 78a80ca3df32ca09a028ccfd76462347df076094..05755362ffcd70d3ba5f21978b152daeaeaa3fbb 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -2457,6 +2457,7 @@ EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_string_padding)
 #ifdef V8_I18N_SUPPORT
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(icu_case_mapping)
 #endif
+EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_async_await)
 
 void InstallPublicSymbol(Factory* factory, Handle<Context> native_context,
                          const char* name, Handle<Symbol> value) {
@@ -3030,6 +3031,7 @@ bool Genesis::InstallExperimentalNatives() {
   static const char* icu_case_mapping_natives[] = {"native icu-case-mapping.js",
                                                    nullptr};
 #endif
+  static const char* harmony_async_await_natives[] = {nullptr};
 
   for (int i = ExperimentalNatives::GetDebuggerCount();
        i < ExperimentalNatives::GetBuiltinsCount(); i++) {