You need to either have your chomium window manually re-sized previously, for which you need to load it once with a proper window manager. Or edit the the file ~/.config/chromium/Default/Preferences (haven't tested it with more than 1 profile) and edit the following section.

"window_placement": { "bottom": 1080, "left": 0, "maximized": true, "right": 1920, "top": 0, "work_area_bottom": 1080, "work_area_left": 0, "work_area_right": 1920, "work_area_top": 0 }