I have a gif file which does not loop infinitely but has a finite number of
repetitions (10 repeats). When I open this in Firefox, Chromium and so on,
it stops after this number of repetitions is reached. See for example the
attached gif image. This the output of "gifsicle -I animg.gif"

* animg.gif 4 images
logical screen 696x472
global color table [8]
background 0
*loop count 10*
+ image #0 696x472
delay 0.10s
+ image #1 696x472
delay 0.10s
+ image #2 696x472
delay 0.10s
+ image #3 696x472
delay 0.10s

When I open this gif file in iceweasel, it loops infinitely, regardless of
the loop count I set, in this case 10. When I open the same image in eog
(eye of gnome) or in Chromium or in Firefox (Ubuntu), it stops correctly
after the 10 repetitions. This bug seems to be inherited from Netscape,
where it was corrected in version Netscape "Atlas" 3.0 b1:
http://www6.uniovi.es/gifanim/gifmakg.htm#loopiterations   "Iteration
counts are now obeyed, giving you finite loops."

I suggest to look at current Firefox code and mimic their implementation
for Iceweasel.

I am using Debian Jessie, namely Linux 3.16.0-4-amd64 #1 SMP Debian
3.16.7-ckt7-1 (2015-03-01) x86_64 GNU/Linux

src:iceweasel has been superseded by src:firefox-esr in version
45.0esr-1 in March 2016. Transitional packages to ease upgrades were
provided in the wheezy, jessie, stretch and buster releases. The
transitional packages have been removed finally before the bullseye
release in August 2021.
After regular security support for buster ended in August 2022 and LTS
support ended in June 2024, I'm closing the remaining bug reports now.

Andreas