The RPi camera is not a webcam. Chromium does not recognize it as a webcam.
But with additional software it can be done.
I haven't done it, but this
looks like a good tutorial.
Introducing Pi-Power-Tools: The All-In-1 Tool for Disk Images and SD Cards.
Boot in a VM, Flash, Mount, Edit, Resize, Repair, even Flash directly from the Internet at twice the speed of any other tool!.