"it would be good to address the handful of TODOs in palette_tray.cc. If any end up being more involved than just re-using existing code elsewhere in the system menu, feel free to spin off separate issues for those and tag them with Proj-MaterialDesign-CrOS."

I will add that by now we should be able to rename palette* to stylus*. The former was chosen for intentional obfuscation, but by now Stylus is used elsewhere in the codebase.