Chrome Platform Status
When the window controls overlay is enabled for installed desktop web apps, the app's client area is extended to cover the entire window--including the title bar area--and the window control buttons (close, maximize/restore, minimize) are overlaid on top of the client area.
https://chromestatus.com/feature/5741247866077184
window-controls-overlay/explainer.md at main · WICG/window-controls-overlay
This document is intended as a starting point for engaging the community and standards bodies in developing collaborative solutions fit for standardization. As the solutions to problems described in this document progress along the standards-track, we will retain this document as an archive and use this section to keep the community up-to-date with the most current standards venue and content location of future work and discussions.
https://github.com/WICG/window-controls-overlay/blob/main/explainer.md

Seonglae Cho