How can I launch FireFox with no window frame or tabs / address bar?

I am looking for a way to launch Firefox from a script or command line without any window frame, address bar, or tabs. I'd like to be able to launch this at a given window size and position on screen.

Illustration:

I'd like to only be able to see the section that is comprised of the red box, and the area inside of it.

Using AutoHotKey in Windows, I've been able to launch FireFox at a given window size / position. However, If I try to launch Firefox in "chromeless" mode, and try to resize the window with AHK, I end up with a 0 px by 0 px browser window.

My AutoHotKey Script:

Run, C:\Program Files\Mozilla Firefox\firefox.exe -chrome http://www.google.com/
WinWait, Mozilla Firefox
WinMove,,,100,100,400,300

I've found related questions, but I've not found a solution:

How can I launch a browser with no window frame or tabs

How can I run Firefox with no tab bar, no top bar, no address bar