Expose well-known Symbols to C++ API.

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index 9093f4dd30d1c1023468da715d84a212953cbd26..35a7e5f4382e80789d17bb6f2a002fbdfcbb8d73 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -6152,43 +6152,57 @@ Local<Symbol> v8::Symbol::New(Isolate* isolate, Local<String> name) {
 }
 
 
-Local<Symbol> v8::Symbol::For(Isolate* isolate, Local<String> name) {
-  i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
-  i::Handle<i::String> i_name = Utils::OpenHandle(*name);
-  i::Handle<i::JSObject> registry = i_isolate->GetSymbolRegistry();
-  i::Handle<i::String> part = i_isolate->factory()->for_string();
+static i::Handle<i::Symbol> SymbolFor(i::Isolate* isolate,
+                                      i::Handle<i::String> name,
+                                      i::Handle<i::String> part) {
+  i::Handle<i::JSObject> registry = isolate->GetSymbolRegistry();
   i::Handle<i::JSObject> symbols =
       i::Handle<i::JSObject>::cast(
           i::Object::GetPropertyOrElement(registry, part).ToHandleChecked());
   i::Handle<i::Object> symbol =
-      i::Object::GetPropertyOrElement(symbols, i_name).ToHandleChecked();
+      i::Object::GetPropertyOrElement(symbols, name).ToHandleChecked();
   if (!symbol->IsSymbol()) {
     DCHECK(symbol->IsUndefined());
-    symbol = i_isolate->factory()->NewSymbol();
-    i::Handle<i::Symbol>::cast(symbol)->set_name(*i_name);
-    i::JSObject::SetProperty(symbols, i_name, symbol, i::STRICT).Assert();
+    symbol = isolate->factory()->NewSymbol();
+    i::Handle<i::Symbol>::cast(symbol)->set_name(*name);
+    i::JSObject::SetProperty(symbols, name, symbol, i::STRICT).Assert();
   }
-  return Utils::ToLocal(i::Handle<i::Symbol>::cast(symbol));
+  return i::Handle<i::Symbol>::cast(symbol);
+}
+
+
+Local<Symbol> v8::Symbol::For(Isolate* isolate, Local<String> name) {
+  i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
+  i::Handle<i::String> i_name = Utils::OpenHandle(*name);
+  i::Handle<i::String> part = i_isolate->factory()->for_string();
+  return Utils::ToLocal(SymbolFor(i_isolate, i_name, part));
 }
 
 
 Local<Symbol> v8::Symbol::ForApi(Isolate* isolate, Local<String> name) {
   i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
   i::Handle<i::String> i_name = Utils::OpenHandle(*name);
-  i::Handle<i::JSObject> registry = i_isolate->GetSymbolRegistry();
   i::Handle<i::String> part = i_isolate->factory()->for_api_string();
-  i::Handle<i::JSObject> symbols =
-      i::Handle<i::JSObject>::cast(
-          i::Object::GetPropertyOrElement(registry, part).ToHandleChecked());
-  i::Handle<i::Object> symbol =
-      i::Object::GetPropertyOrElement(symbols, i_name).ToHandleChecked();
-  if (!symbol->IsSymbol()) {
-    DCHECK(symbol->IsUndefined());
-    symbol = i_isolate->factory()->NewSymbol();
-    i::Handle<i::Symbol>::cast(symbol)->set_name(*i_name);
-    i::JSObject::SetProperty(symbols, i_name, symbol, i::STRICT).Assert();
-  }
-  return Utils::ToLocal(i::Handle<i::Symbol>::cast(symbol));
+  return Utils::ToLocal(SymbolFor(i_isolate, i_name, part));
+}
+
+
+static Local<Symbol> GetWellKnownSymbol(Isolate* isolate, const char* name) {
+  i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
+  i::Handle<i::String> i_name =
+      Utils::OpenHandle(*String::NewFromUtf8(isolate, name));
+  i::Handle<i::String> part = i_isolate->factory()->for_intern_string();
+  return Utils::ToLocal(SymbolFor(i_isolate, i_name, part));
+}
+
+
+Local<Symbol> v8::Symbol::GetIterator(Isolate* isolate) {
+  return GetWellKnownSymbol(isolate, "Symbol.iterator");
+}
+
+
+Local<Symbol> v8::Symbol::GetUnscopables(Isolate* isolate) {
+  return GetWellKnownSymbol(isolate, "Symbol.unscopables");
 }