Do this by deleting code after calls to V8_Fatal() (either through
UNREACHABLE() or FATAL()). Comments suggest that the returns there
were needed to make a compiler happy, but all compilers seem to be
happy with this change too. My guess is that either
https://codereview.chromium.org/1393023003 which marked V8_Fatal()
as noreturn, or https://chromium-review.googlesource.com/#/c/544845/
which switched to the C++11 spelling of noreturn, fixed the warnings
that the explicit code after V8_Fatal() was supposed to silence.

There's one more warning in src/compiler/machine-graph-verifier.cc,
but fixing that changes behavior.  I asked about that one in
https://codereview.chromium.org/2573573004/#msg27 instead.

Bug: chromium:346399
Change-Id: Ie9519d5432bdeaaf382e8390d8254d3b79e622e4
Reviewed-on: https://chromium-review.googlesource.com/669803Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48092}