I only hope they're also getting rid of GTK icons on the main chrome. They make (unthemed) Firefox on a high-DPI screen completely unusable.
(Why? Scaling up page content (via layout.css.devPixelsPerPx) also scales up chrome, including the (already properly sized) icons— so every icon in Fx ends up being four times larger than it should.)
(Why? Scaling up page content (via layout.css.devPixelsPerPx) also scales up chrome, including the (already properly sized) icons— so every icon in Fx ends up being four times larger than it should.)