Fix possible loss of data warnings in media_unittests

Fix possible loss of data warnings in media_unittests

Fix compiler warning about size_t to uint8_t conversion.

BUG=

Committed: https://crrev.com/55db6378d34777454c9ee6f8a3d0e3b93e507b80
Cr-Commit-Position: refs/heads/master@{#367491}

[Tomasz Moniuszko, 2016-01-04 16:09:53]

tmoniuszko@opera.com changed reviewers:
+ sandersd@chromium.org

[sandersd (OOO until July 31), 2016-01-04 19:37:25]

lgtm

[Tomasz Moniuszko, 2016-01-05 07:06:27]

The CQ bit was checked by tmoniuszko@opera.com

[commit-bot: I haz the power, 2016-01-05 07:06:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1559013002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1559013002/1

[commit-bot: I haz the power, 2016-01-05 07:36:30]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-01-05 07:37:28]

Description was changed from

==========
Fix possible loss of data warnings in media_unittests

Fix compiler warning about size_t to uint8_t conversion.

BUG=
==========

to

==========
Fix possible loss of data warnings in media_unittests

Fix compiler warning about size_t to uint8_t conversion.

BUG=

Committed: https://crrev.com/55db6378d34777454c9ee6f8a3d0e3b93e507b80
Cr-Commit-Position: refs/heads/master@{#367491}
==========

[commit-bot: I haz the power, 2016-01-05 07:37:29]

Patchset 1 (id:??) landed as
https://crrev.com/55db6378d34777454c9ee6f8a3d0e3b93e507b80
Cr-Commit-Position: refs/heads/master@{#367491}