Several ideas where suggested on slack for enabling PHC more widely. Mainly we want to be able to enable it in a more "dynamic" way so it can be used easily in beta and eventually release.

• Enable PHC probabilistically for the parent process (maybe?)
• Enable PHC probabilistically for GPU/socket/etc processes.
• Enable PHC probabilistically for at most one content process - but make it more aggressive for this process.
• Make PHC less aggressive for computers with less than 8GB memory.
• Disable PHC for computers with less than 4GB memory.
• Maybe enabling PHC via Normandy.

All of this means making the decision dynamic and probably controlled by the parent process. PHC should be able to detect its process type, but will also need another way to control the chance of enabling it and how to ensure at most one content process has it. That could be an environment variable, IPC or something, I think it's unclear what's best right now.