Explicitly call out where overflows are expected, and add appropriate
checking for them.
BUG=b:235999011
TEST=Unittests on CrOS and Linux
Change-Id: I999a6996183c2f4afc16a1c0188dee3bd64d7f09
Reviewed-on: https://chromium-review.googlesource.com/c/breakpad/breakpad/+/3759630
Reviewed-by: Mike Frysinger <vapier@chromium.org>