Any sufficiently advanced web browser is indistinguishable from an operating system.
How are these two things related? One is for running code in a VM, and the other is a UX pattern for presenting multiple screens/interfaces for multitasking.
[0] https://www.openhub.net/p/Linux/analyses/latest/languages_su...
[1] https://www.openhub.net/p/WebKit/analyses/latest/languages_s...