As Dirk and I discussed on IRC, we should have --timeout <timeout> option in each port's DRT.
This will allow DRT to gracefully timeout instead of webkit.py detecting the timeout and restarting DRT.
Note that this does not replace the timer in webkit.py; we still need that to protect against a failing DRT (as we see on Chromium, which doesn't have the timer in chromium.py; see bug 74039).
A partial motivation for this is that since the non-chromium DRTs have hard-coded watchdog timers, long --time-out-ms values don't work correctly. That's bad.
This will also allow us to clean up the no_timeout parameter added to the Driver interface in bug 76612.