If we'd port Android MemoryObserver.js, this line should be removed. Currently, I don't see much help porting that as it doesn't do anything else than gc() and zombification of tabs. GC can be done through "heap-minimize" and zombification should be done at browser side.

See,
https://github.com/tmeshkova/gecko-dev/blob/embedlite/embedding/embedlite/embedding.js#L225