Cherry pick underflow fix.

Cherry pick underflow fix.

BUG=583607
Committed: https://crrev.com/7716418a27d561ee295a99f11fd3865580748de2
Cr-Commit-Position: refs/heads/master@{#373736}

[eustas, 2016-02-04 16:50:49]

eustas@chromium.org changed reviewers:
+ bashi@chromium.org, ksakamoto@chromium.org

[bashi, 2016-02-04 23:22:22]

Could you explain why do you cherry-pick it instead of updating to
37a320dd81db8d546cd24a45b4c61d87b45dcade?

[Kunihiko Sakamoto, 2016-02-05 01:49:20]

I think this patch is intended to be merged to M49, so cherrypick lgtm.

(It'd be great if you could update M50 in sync with the github latest revision,
in a follow-up patch.)

[Kunihiko Sakamoto, 2016-02-05 01:51:32]

The CQ bit was checked by ksakamoto@chromium.org

[commit-bot: I haz the power, 2016-02-05 01:52:38]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1662313002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1662313002/1

[commit-bot: I haz the power, 2016-02-05 03:17:52]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-02-05 03:18:30]

Description was changed from

==========
Cherry pick underflow fix.

BUG=583607
==========

to

==========
Cherry pick underflow fix.

BUG=583607

Committed: https://crrev.com/7716418a27d561ee295a99f11fd3865580748de2
Cr-Commit-Position: refs/heads/master@{#373736}
==========

[commit-bot: I haz the power, 2016-02-05 03:18:30]

Patchset 1 (id:??) landed as
https://crrev.com/7716418a27d561ee295a99f11fd3865580748de2
Cr-Commit-Position: refs/heads/master@{#373736}