Controls whether unload event handlers can be disabled.

Description

unload event handlers are being deprecated. Whether they fire depends on the unload Permissions-Policy. Currently, the policy allows them by default. In the future, they move to being disallowed by default, and sites must explicitly enable them using Permissions-Policy headers. This enterprise policy can be used to opt out of this gradual deprecation by forcing the default to stay enabled. Pages might depend on unload event handlers to save data or to signal the end of a user session to the server. This dependency isn't recommended because it's unreliable and impacts performance by blocking use of BackForwardCache. Recommended alternatives exist, but the unload event has been used for a long time. Some applications might still rely on them. If you disable this policy or don't configure it, unload event handlers are gradually deprecated in-line with the deprecation rollout, and sites that don't set Permissions-Policy header stop firing `unload` events. If you enable this policy, the unload event handlers continue to work by default.