This task was originally included under  crbug.com/680809  however we have decided to ship that API w/o this feature and follow up with it later.  As it stands the KeyboardLock API on MacOS allows for intercepting browser shortcuts but not system level shortcuts.

The reason for this is due to the underlying APIs provided by MacOS, specifically the Quartz event APIs.  MacOS provides a similar hooking pattern to Windows using CGEventTapCreate(https://developer.apple.com/documentation/coregraphics/1454426-cgeventtapcreate?language=objc) however it has an additional requirement which is that the application be manually added to a list of accessibility applications in the Mac system / control panel.

This is not something we want users to do so there will need to be some additional design work to address this issue in order to get the functionality we want on MacOS.