Similar to D10781: Replace manual palette adjustment with background role (fullscreen info label), modifying background role to get a dark background instead of
manually adjusting palette is a preferred solution. This way the palette is still
inherited so does not need to be continually adjusted when the overall palette
changes, like when switching to/from fullscreen.
This also makes the entire fullscreen toolbar (including URL nav) have a consistent background color
Fullscreen left edge before:
Fullscreen left edge after:
Fullscreen right edge before:
Fullscreen right edge after: