The current bindings use the same callback code in main world, isolated world and (potentially) workers. When called, the callback needs to figure out in which of these 3 types of context we are, and that's a performance hit. See DomDataStore::current() which contains the logic for figuring this out.
We'd like to add a possibility to selectively generate different callback functions for these three cases, so that we know, call-time, in which of the 3 cases we are in, and we don't need to execute any code for figuring it out.
Closing some V8-related work items.