EDIT: I was able to get it to work, by following the advice in this thread.
Is there anyone out there who has any idea on what to do if I want to be able to run firefox (or chromium) without a SDCARD in the device, without the browser crashing?
So far I tried
First I start firefox, then I physically remove the SDCARD, then firefox crashes (only happens if SDCARD is removed and 100% reproducible). The error output reads "Segmentation fault".
I run "ps", then run "fuser -m /dev/mmcblk0p2" and see that firefox is using /mnt/mmcblk0p2. I try "umount -f /dev/mmcblk0p2" buy get a device busy error.
I then add firefox to copy2fs.lst and noswap to config, but firefox still crashes if I remove the SDCARD.
I then run "sudo umount -a" and now /dev/mmcblk0p2 gets unmounted. But firefox will crash after a while. This time it will take longer time (still measured in minutes) before it crashes, but it will crash eventually.
If I haven't started Firefox I can not start it after having un-mounted mmcblk0p2, but if I have started it, it seems to be still in RAM because I can restart it again after the crash, but will eventually crash never the less.