Add support for adding VideoSinks to VideoTracks.

Add support for adding VideoSinks to VideoTracks.

VideoSinks receive the new kind of VideoFrames and will replace
VideoRenderers. Converting from old texture frames to VideoFrames will
involve conversion to I420 so it is not recommended to use VideoSinks
before all sources produce VideoFrames.

BUG=webrtc:7749, webrtc:7760
Review-Url: https://codereview.webrtc.org/3002553002
Cr-Commit-Position: refs/heads/master@{#19335}
Committed: https://chromium.googlesource.com/external/webrtc/+/0ba43b5a2045b0b6de4c8e374895462961330b85

[sakal, 2017-08-14 11:17:51]

sakal@webrtc.org changed reviewers:
+ kthelgason@webrtc.org

[sakal, 2017-08-14 11:17:51]

PTAL

[kthelgason, 2017-08-14 11:37:19]

looks legit, lgtm

[sakal, 2017-08-14 11:39:09]

The CQ bit was checked by sakal@webrtc.org

[commit-bot: I haz the power, 2017-08-14 11:39:16]

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, 2017-08-14 12:17:49]

CQ is committing da patch.

Bot data: {"patchset_id": 20001, "attempt_start_ts": 1502710749929780,
"parent_rev": "dc5fc82c626e1848ca1a40d7e388b87bf369d881", "commit_rev":
"0ba43b5a2045b0b6de4c8e374895462961330b85"}

[commit-bot: I haz the power, 2017-08-14 12:17:57]

Description was changed from

==========
Add support for adding VideoSinks to VideoTracks.

VideoSinks receive the new kind of VideoFrames and will replace
VideoRenderers. Converting from old texture frames to VideoFrames will
involve conversion to I420 so it is not recommended to use VideoSinks
before all sources produce VideoFrames.

BUG=webrtc:7749, webrtc:7760
==========

to

==========
Add support for adding VideoSinks to VideoTracks.

VideoSinks receive the new kind of VideoFrames and will replace
VideoRenderers. Converting from old texture frames to VideoFrames will
involve conversion to I420 so it is not recommended to use VideoSinks
before all sources produce VideoFrames.

BUG=webrtc:7749, webrtc:7760

Review-Url: https://codereview.webrtc.org/3002553002
Cr-Commit-Position: refs/heads/master@{#19335}
Committed:
https://chromium.googlesource.com/external/webrtc/+/0ba43b5a2045b0b6de4c8e374...
==========

[commit-bot: I haz the power, 2017-08-14 12:17:58]

Committed patchset #2 (id:20001) as
https://chromium.googlesource.com/external/webrtc/+/0ba43b5a2045b0b6de4c8e374...