Fix an implicit narrowing conversion found by MSVC

Fix an implicit narrowing conversion found by MSVC

BUG=none

Review-Url: https://codereview.webrtc.org/2999363002
Cr-Commit-Position: refs/heads/master@{#19444}
Committed: https://chromium.googlesource.com/external/webrtc/+/2a596549ca6fba655727dbf24505c75711920340

[kwiberg-webrtc, 2017-08-22 08:45:14]

The CQ bit was checked by kwiberg@webrtc.org to run a CQ dry run

[commit-bot: I haz the power, 2017-08-22 08:45:19]

Dry run: CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.webrtc.org/...

[kwiberg-webrtc, 2017-08-22 09:13:42]

kwiberg@webrtc.org changed reviewers:
+ charujain@webrtc.org

[commit-bot: I haz the power, 2017-08-22 09:15:07]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-08-22 09:15:08]

Dry run: This issue passed the CQ dry run.

[charujain, 2017-08-22 10:36:27]

lgtm

[kwiberg-webrtc, 2017-08-22 10:40:39]

The CQ bit was checked by kwiberg@webrtc.org

[commit-bot: I haz the power, 2017-08-22 10:40:48]

CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.webrtc.org/...

[commit-bot: I haz the power, 2017-08-22 10:43:29]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1503398439707310, "parent_rev":
"4553562fe3be5e61ebde13dd2c0850cbce49d052", "commit_rev":
"2a596549ca6fba655727dbf24505c75711920340"}

[commit-bot: I haz the power, 2017-08-22 10:43:34]

Description was changed from

==========
Fix an implicit narrowing conversion found by MSVC

BUG=none
==========

to

==========
Fix an implicit narrowing conversion found by MSVC

BUG=none

Review-Url: https://codereview.webrtc.org/2999363002
Cr-Commit-Position: refs/heads/master@{#19444}
Committed:
https://chromium.googlesource.com/external/webrtc/+/2a596549ca6fba655727dbf24...
==========

[commit-bot: I haz the power, 2017-08-22 10:43:35]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/external/webrtc/+/2a596549ca6fba655727dbf24...