Added a workaround for undefined behavior.

Added a workaround for undefined behavior.

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

Committed: https://crrev.com/49c3864b4b8348a66a93f042324ae4c35d04c0c4
Cr-Commit-Position: refs/heads/master@{#27100}

[Sven Panne, 2015-03-10 12:11:08]

Patchset #2 (id:20001) has been deleted

[Sven Panne, 2015-03-10 12:11:34]

svenpanne@chromium.org changed reviewers:
+ dcarney@chromium.org

[dcarney, 2015-03-10 12:12:09]

lgtm

[Sven Panne, 2015-03-10 12:13:07]

Committed patchset #1 (id:1) manually as
49c3864b4b8348a66a93f042324ae4c35d04c0c4 (presubmit successful).

[commit-bot: I haz the power, 2015-03-10 12:13:07]

Patchset 1 (id:??) landed as
https://crrev.com/49c3864b4b8348a66a93f042324ae4c35d04c0c4
Cr-Commit-Position: refs/heads/master@{#27100}