Inconsistency: different permissions can be optional permissions across browsers

[bershanskiy]

Background

Browsers gate some powerful APIs behind permissions which generate warnings. See Chromium warnings, for example. Extensions also can use manifest.json optional permissions to avoid install-time warnings and instead to request the required permissions as needed, in context which follows the best-practices and the [Principle of least privilege](https://en.wikipedia.org/wiki/Principle_of_least_privilege].

However, not all permissions can be optional (MDN table for reference)

Proposal

Subjectively, I believe that all permissions can and should be optional. Some APIs can be made to throw an error with appropriate explanation or for compatibility reasons turned into no-ops (the APIs exist and pretend to work the way they usually do, but in reality have no effect).