bug#23431: 25.0.93; EWW hangs

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: jch@pps.univ-paris-diderot.fr,  23431@debbugs.gnu.org
> Date: Tue, 03 May 2016 19:04:21 +0200
> 
> Most parts of the image formatting doesn't happen until redisplay
> happens -- `image-animate-timeout' just increases the image index, and
> then redisplay does all the hard lifting.
> 
> While redisplay is doing all that, Emacs isn't allowing any events to
> fire, I think, so we should be able to see that Emacs is busy...

But why would display of an image be so slow?  It isn't slow with
simple GIF images.  What am I missing?