[xmonad] update: chromium slow redraw

[Carsten Mattner]

Due to my local xmonad --recompile breakage I had to fall back to dwm and
was surprised to see that the very slow non-floating Chromium window
redraw evident in XMonad since Chromium switched to Aura does NOT
happen in dwm.

Any idea what's different in the dwm X11 code that doesn't make Chromium
window (content) redraws super visible (slow)?