Replace VideoStream::SizeCallback with VideoStream::Observer interface.

Replace VideoStream::SizeCallback with VideoStream::Observer interface.

The new Observer interface will allow to notify ClientSession when a
video frame is sent, which will allow to provide the client with the
frame_id->event_timestamp mapping.

BUG=621691
Committed: https://crrev.com/ad51be89ed73cc6cdf56418ee9193a3a628b1f44
Cr-Commit-Position: refs/heads/master@{#401214}

[Sergey Ulanov, 2016-06-20 22:38:21]

sergeyu@chromium.org changed reviewers:
+ jamiewalch@chromium.org

[Jamie, 2016-06-20 22:58:41]

lgtm

[Sergey Ulanov, 2016-06-22 05:21:01]

The CQ bit was checked by sergeyu@chromium.org

[commit-bot: I haz the power, 2016-06-22 05:21:11]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2083843002/1

[commit-bot: I haz the power, 2016-06-22 06:05:02]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-06-22 06:07:22]

Description was changed from

==========
Replace VideoStream::SizeCallback with VideoStream::Observer interface.

The new Observer interface will allow to notify ClientSession when a
video frame is sent, which will allow to provide the client with the
frame_id->event_timestamp mapping.

BUG=621691
==========

to

==========
Replace VideoStream::SizeCallback with VideoStream::Observer interface.

The new Observer interface will allow to notify ClientSession when a
video frame is sent, which will allow to provide the client with the
frame_id->event_timestamp mapping.

BUG=621691

Committed: https://crrev.com/ad51be89ed73cc6cdf56418ee9193a3a628b1f44
Cr-Commit-Position: refs/heads/master@{#401214}
==========

[commit-bot: I haz the power, 2016-06-22 06:07:23]

Patchset 1 (id:??) landed as
https://crrev.com/ad51be89ed73cc6cdf56418ee9193a3a628b1f44
Cr-Commit-Position: refs/heads/master@{#401214}