Inconsistency: incognito in proxy.settings

[erosman]

Firefox proxy.settings requires incognito permission.

Changing proxy settings requires private browsing window access because proxy settings affect private and non-private windows. Whether an extension can access private browsing windows is under user control. For details, see Extensions in Private Browsing. Your extension can check whether it can access private browsing windows using extension.isAllowedIncognitoAccess. If your extension does not have private window permission, calls to proxy.settings.set() throw an exception.

Chrome chrome.proxy does not have the same requirement.

Other browsers have not been checked.