Support multiple video decoders and encoders

Support multiple video decoders and encoders

Some platforms have multiple video decoders and encoders.
For decode and encoder, return the first succeed initialized VDA and VEA
from all possible platforms. GetSupportedProfile return all possible
profiles from all encoders.

This cl is submitted again because crrev.com/826663002 was reverted in
crrev.com/832383004.

BUG=445016
TEST=Tested on squawks. For decoder, make sure V4L2 initialization
failed and VAAPI successed. For encoder, test on extension.

TBR=piman@chromium.org,posciak@chromium.org

Committed: https://crrev.com/712f1acaf22f225a5eaef28b3dff9aecb7bc5cc8
Cr-Commit-Position: refs/heads/master@{#310754}

[henryhsu, 2015-01-09 07:00:11]

henryhsu@chromium.org changed reviewers:
+ wuchengli@chromium.org

[wuchengli, 2015-01-09 07:06:59]

LGTM

[piman, 2015-01-09 07:19:34]

lgtm

[henryhsu, 2015-01-09 09:51:07]

The CQ bit was checked by henryhsu@chromium.org

[commit-bot: I haz the power, 2015-01-09 09:51:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/842123002/20001

[commit-bot: I haz the power, 2015-01-09 11:26:16]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-01-09 11:27:09]

Patchset 2 (id:??) landed as
https://crrev.com/712f1acaf22f225a5eaef28b3dff9aecb7bc5cc8
Cr-Commit-Position: refs/heads/master@{#310754}