Custom chromium with fixed window

Hello
I need custom chromium with fixed window
I need a browser custom from chromium and this browser have fixed window size.
I want have custom command argument like this --window-fixed-size=800,600
and i want release full document explan how to make this feature
Video Demo
https://youtu.be/TnLN79eqvBE
DOcument build chromium
https://chromium.googlesource.com/chromium/src/+/main/docs/windows_build_instructions.md