[es6] implement default parameters via desugaring

src/bootstrapper.cc

Index: src/bootstrapper.cc
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index cec7e9e7d21f83a5bb664b4809f711d9a4d00cb4..b946917743a9c5f47e0beafe1d09ab47a2b5c760 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -1694,6 +1694,7 @@ EMPTY_NATIVE_FUNCTIONS_FOR_FEATURE(harmony_reflect)
 EMPTY_NATIVE_FUNCTIONS_FOR_FEATURE(harmony_spreadcalls)
 EMPTY_NATIVE_FUNCTIONS_FOR_FEATURE(harmony_destructuring)
 EMPTY_NATIVE_FUNCTIONS_FOR_FEATURE(harmony_object)
+EMPTY_NATIVE_FUNCTIONS_FOR_FEATURE(harmony_optional_params)
 
 
 void Genesis::InstallNativeFunctions_harmony_proxies() {
@@ -1724,6 +1725,7 @@ EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_rest_parameters)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_spreadcalls)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_destructuring)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_object)
+EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_optional_params)
 
 void Genesis::InitializeGlobal_harmony_regexps() {
   Handle<JSObject> builtins(native_context()->builtins());
@@ -2332,6 +2334,7 @@ bool Genesis::InstallExperimentalNatives() {
   static const char* harmony_destructuring_natives[] = {nullptr};
   static const char* harmony_object_natives[] = {"native harmony-object.js",
                                                  NULL};
+  static const char* harmony_optional_params_natives[] = {nullptr};
 
   for (int i = ExperimentalNatives::GetDebuggerCount();
        i < ExperimentalNatives::GetBuiltinsCount(); i++) {