The Mozilla Hacks blog covers some recent Firefox changes that will allow code from web sites to use shared memory and high-resolution timers in a (hopefully) safe manner. "Together with others in the WHATWG community, we designed a set of headers that meet these requirements.
The Cross-Origin-Opener-Policy header allows you to process-isolate yourself from attackers. It also has the desirable effect that attackers cannot have access to your global object if they were to open you in a popup. This prevents XS-Leaks and various navigation attacks. Adopt this header even if you have no intention of using shared memory!"