Introduce extras export object.

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index 4ad40423b13ccb21ecfb03540682c6c5cd94d838..0cd34a116cc81758876f00d71bdf2ad9d2065cb4 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -5493,6 +5493,16 @@ void Context::DetachGlobal() {
 }
 
 
+MaybeLocal<v8::Object> Context::GetExtrasExportsObject() {
+  i::Handle<i::Context> context = Utils::OpenHandle(this);
+  i::Isolate* isolate = context->GetIsolate();
+  i::Object* extras_exports = context->extras_exports_object();
+  if (!extras_exports->IsJSObject()) return MaybeLocal<v8::Object>();
+  i::Handle<i::JSObject> exports(i::JSObject::cast(extras_exports), isolate);
+  return Utils::ToLocal(exports);
+}
+
+
 void Context::AllowCodeGenerationFromStrings(bool allow) {
   i::Handle<i::Context> context = Utils::OpenHandle(this);
   i::Isolate* isolate = context->GetIsolate();