Implement ES6 completion semantics (--harmony-completion).

src/bootstrapper.cc

Index: src/bootstrapper.cc
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index be2f58e8754783763333d37ecf6b88e172dc9454..323165caa87727c6c8b305b074f4fff423a3742a 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -1879,6 +1879,7 @@ EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_concat_spreadable)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_regexps)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_unicode_regexps)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_tostring)
+EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_completion)
 
 
 void Genesis::InitializeGlobal_harmony_tolength() {
@@ -2587,6 +2588,7 @@ bool Genesis::InstallExperimentalNatives() {
   static const char* harmony_simd_natives[] = {"native harmony-simd.js",
                                                nullptr};
   static const char* harmony_tolength_natives[] = {nullptr};
+  static const char* harmony_completion_natives[] = {nullptr};
 
   for (int i = ExperimentalNatives::GetDebuggerCount();
        i < ExperimentalNatives::GetBuiltinsCount(); i++) {