Note that this patch is not really a *solution*, it is just enough to
make the undefined behavior unobservable. The real fix would be being
much more correct about sizes and signedness in our code base...

BUG=chromium:464657
LOG=n
R=dcarney@chromium.org

Review URL: https://codereview.chromium.org/995743002

Cr-Commit-Position: refs/heads/master@{#27100}