Comment # 3 on bug 1180802 from Takashi Iwai

Looks like a rendering bug.  But OTOH I wonder how it could be recorded in the
screen shot.  You started a screen shot program and get the image, not taking
the picture via camera or such, right?

Does this happen always?  Also, if you redraw or move window at the blank
region, is it drawn?  Or still blank?