The engine roll here #156562 was reverted for consistent failures in the framework postsubmit test Linux_mokey flutter_gallery__back_button_memory

https://ci.chromium.org/ui/p/flutter/builders/prod/Linux_mokey%20flutter_gallery__back_button_memory/1629/overview

Wondering if flutter/engine#55810 was related @jonahwilliams

P0 since this is blocking the engine -> framework roll.