[es7] implement exponentiation operator proposal

src/bootstrapper.cc

Index: src/bootstrapper.cc
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index 4d042ea3c66d702df788f00dcaf797b0241808eb..3d7f6cc13df3a9aba190cb80fb1008383549f268 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -2321,6 +2321,7 @@ EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_function_name)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_function_sent)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(promise_extra)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_tailcalls)
+EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_exponentiation_operator)
 
 void InstallPublicSymbol(Factory* factory, Handle<Context> native_context,
                          const char* name, Handle<Symbol> value) {
@@ -2968,6 +2969,7 @@ bool Genesis::InstallExperimentalNatives() {
   static const char* harmony_object_values_entries_natives[] = {nullptr};
   static const char* harmony_object_own_property_descriptors_natives[] = {
       nullptr};
+  static const char* harmony_exponentiation_operator_natives[] = {nullptr};
 
   for (int i = ExperimentalNatives::GetDebuggerCount();
        i < ExperimentalNatives::GetBuiltinsCount(); i++) {