Add a --harmony-species flag, defining @@species on constructors

src/bootstrapper.cc

Index: src/bootstrapper.cc
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index 93a8b44cc76a20f5ead4c98ab508910aa5fac607..9d74620af406b0cfbdbe9dd973777de517f8f2b0 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -2117,6 +2117,7 @@ void Bootstrapper::ExportExperimentalFromRuntime(Isolate* isolate,
 
   INITIALIZE_FLAG(FLAG_harmony_tostring)
   INITIALIZE_FLAG(FLAG_harmony_tolength)
+  INITIALIZE_FLAG(FLAG_harmony_species)
 
 #undef INITIALIZE_FLAG
 }
@@ -2334,6 +2335,13 @@ void Genesis::InitializeGlobal_harmony_proxies() {
 }
 
 
+void Genesis::InitializeGlobal_harmony_species() {
+  if (!FLAG_harmony_species) return;
+  InstallPublicSymbol(factory(), native_context(), "species",
+                      factory()->species_symbol());
+}
+
+
 Handle<JSFunction> Genesis::InstallInternalArray(Handle<JSObject> target,
                                                  const char* name,
                                                  ElementsKind elements_kind) {
@@ -2665,6 +2673,8 @@ bool Genesis::InstallExperimentalNatives() {
   static const char* harmony_sloppy_natives[] = {nullptr};
   static const char* harmony_sloppy_function_natives[] = {nullptr};
   static const char* harmony_sloppy_let_natives[] = {nullptr};
+  static const char* harmony_species_natives[] = {"native harmony-species.js",
+                                                  nullptr};
   static const char* harmony_unicode_regexps_natives[] = {
       "native harmony-unicode-regexps.js", nullptr};
   static const char* harmony_default_parameters_natives[] = {nullptr};