[Extensions] Don't allow gin::Define to be overridden

gin/converter.h

Index: gin/converter.h
diff --git a/gin/converter.h b/gin/converter.h
index 8d17d41c29fba56bd5bae0a66d895f7cd035d79b..12348e2d852724dccd90d04f0cd2dbe1103ca91f 100644
--- a/gin/converter.h
+++ b/gin/converter.h
@@ -20,7 +20,8 @@ bool SetProperty(v8::Isolate* isolate,
                  v8::Local<v8::Object> object,
                  KeyType key,
                  v8::Local<v8::Value> value) {
-  auto maybe = object->Set(isolate->GetCurrentContext(), key, value);
+  auto maybe =
+      object->DefineOwnProperty(isolate->GetCurrentContext(), key, value);
   return !maybe.IsNothing() && maybe.FromJust();
 }