Most users of the macro were ignoring the regex, now it makes sure a DCHECK
caused the death (message contains "Check failed") without adding burden on
callers to encode the exact error message.

This catched an error in SchedulerLock which was generating an exception in
std::unordered_map::at() instead of hitting the DCHECK it was intending to
hit. Fixed in precursor CL @ https://codereview.chromium.org/2218443002/.

Also caught http://crbug.com/634552, disabled TaskSchedulerTaskTrackerTest.SingletonAllowed's
death test on OS_LINUX for now because of it.

Also updated thread_restrictions.cc to use NOTREACHED() instead of LOG(FATAL)
in order for it to generate a DCHECK failure (it's only defined when DCHECK_IS_ON()
so it makes sense to align it with that).

BUG=553459, 634552

Review-Url: https://codereview.chromium.org/2213933003
Cr-Commit-Position: refs/heads/master@{#409980}