--I--
For correct operation, shared memory support has to be enabled
in Chromium by performing the following command as root :

# sysctl kern.ipc.shm_allow_removed=1

To preserve this setting across reboots, append the following
to /etc/sysctl.conf :

kern.ipc.shm_allow_removed=1

FreeBSD 11.0-R and newer have this set by default.

--II--
Chromium has a known problem of hanging tabs. The workaround
for this problem is to mount ~/.cache/chromium as memory-fs.
In order to do this, before you run chromium, please run these
commands once as root for each user who uses chromium (replace
{user}/{group} with your user/group names):

# [ -d ~{user}/.cache/chromium ] || mkdir ~{user}/.cache/chromium
# echo "md $(echo ~{user})/.cache/chromium mfs rw,late,-w{user}:{group},-s300m 2 0" >> /etc/fstab
# mount ~{user}/.cache/chromium
