More patches that match to a bugzilla.mozilla.org bug:
040_netwerk_buffer_count.diff bug 401836 (unclear if we still need this, too many changes to the networking code to tell where this code has moved to)
675_unknown_protocol_handling.diff bug 401848 (fix never committed, looks easy to forward-port)
GConfProxySettings.diff bug 458211 (fix never committed, dont know if we still need it, can't find where the relavent code has moved to)
020_BUG349921_toolkit_branding.diff bug 401851 (build system has been changed so much in FF24 its unclear if this is needed or not)
JSBreakExperimental.diff bug 449109 (fix never committed, looks easy to forward-port)
150_attachment.cgi?id=342275.diff bug 459078 (fix never committed, dont know if we still need it, can't find where the relavent code has moved to)
854ab30d101e.diff bug 513544 (already in FF24)
92422.workaround.diff bug 469667 (fix never committed, looks easy to forward-port)
attachment.cgi?id=408390.diff bug 485252 (already in FF24)
attachment.cgi?id=418542.diff bug 536031 (already in FF24)
attachment.cgi?id=419012.diff bug 536560 (already in FF24)
attachment.cgi?id=419536.diff bug 507811 (already in FF24)
attachment.cgi?id=45208.diff bug 532626 (fix never committed, dont know if we still need it, can't find where the relavent code has moved to)
attachment.cgi?id=45209.diff bug 532627 (already in FF24)
attachment.cgi?id=46259.diff bug 488046 (already in FF24)
BMO530075_connectivity_ui_fix.diff bug 530075 (fix never committed, looks easy to forward-port)
bug137606.diff bug 523941 (fix never committed, doesn't look important since its just string changes)
bug143563.diff bug 532612 (already in FF24)
bug491722.diff bug 491722 (already in FF24)
bug505018.jemalloc.diff bug 505918 (related to the now removed gtk embedding stuff, will need to be sorted out as part of bringing that back)
Bug513630.workaround.diff bug 513630 (related to the now removed gtk embedding stuff, will need to be sorted out as part of bringing that back)
bug513736.wr.diff bug 513736 (already in FF24)
bug533950_wr.diff bug 533950 (fix never committed, dont know if we still need it, can't find where the relavent code has moved to)
bug546074.diff bug 546074 (already in FF24)
bug588724.diff bug 588724 (fix never committed, looks easy to forward-port)
CheckCompatibilitySave.diff bug 532620 (fix never committed, the relavent code is gone now so we dont need this I guess)
conic.diff bug 532072 (already in FF24)
connectivity.diff bug 532078 (fix never committed, looks easy to forward-port)
DBFlush_systemIdle.diff bug 518804 (already in FF24)
disable_refresh_in_bg.diff bug 518805 (fix never committed, looks easy to forward-port)
enable_16bpp_format.diff bug 386440 (unclear from the bug if its in FF24 or not or what we need to do about it)
gnomevfs_ext_without_gnomevfs.diff bug 532621 (already in FF24)
hildon_mime_missing.diff bug 532610 (seems to not be required anymore due to other code changes)
idleservicetimer.diff bug 559784 (seems to not be required anymore due to other code changes)
LowMemoryManageImprovements.diff bug 532623 (seems to not be required anymore due to other code changes)
nb128288.diff bug 532614 (already in FF24)
nolibxul_pkgconfig.diff bug 482104 (fix never committed, looks easy to forward-port)
osso-mem.diff bug 532608 (already in FF24)
UICallback_CC.diff bug 508518 (already in FF24)
watchdog.diff bug 477850 (seems to not be required anymore due to other code changes)

"already in FF24" means the patch was committed to mozilla-central with a milestone that pre-dates FF24 and therefore the fix doesn't need to be applied.

There are a total of 47 patches that I can match to a bugzilla.mozilla.org bug (all of which I have mentioned here).

I suspect all of the remaining 67 patches will need to be manually checked (figure out if they need to be forward ported to FF24, rewritten to do something totally different or just ignored)