here's plain (in a good way:) webkit: https://surf.suckless.org
First launch: 0 bytes.
The note at the top of surf's page about the lack of tabs is missing some context, surf is composable, so if you want tabs, it comes with a script to use tabbed. Each window (or tab) runs in it's own process (skipping some details). It's also easy to enable/disable JS (per process) out of the box with it's keybindings.
Manpage: http://dpaste.com/1R3Q242.txt