[test][rtcp] Added function for parsing single rtcp packet in tests.

Added function for parsing single rtcp packet in tests.

BUG=webrtc:5260
R=pbos@webrtc.org

Committed: https://crrev.com/b4c82474be64b815141284e37a188b998dc45fb5
Cr-Commit-Position: refs/heads/master@{#12033}

[danilchap, 2016-03-17 09:58:17]

danilchap@webrtc.org changed reviewers:
+ pbos@webrtc.org

[danilchap, 2016-03-17 09:58:17]

Sample usage could be found in this CL:
https://codereview.webrtc.org/1806073002/

This function is not meaningful for production code because
it assumes too much about incoming buffer.
But it is common for test code: each rtcp test file define this function in one
way or another.

[pbos-webrtc, 2016-03-17 12:13:46]

lgtm

[danilchap, 2016-03-17 12:15:24]

Description was changed from

==========
Added function for parsing single rtcp packet in tests.

BUG=webrtc:5260
==========

to

==========
Added function for parsing single rtcp packet in tests.

BUG=webrtc:5260
R=pbos@webrtc.org

Committed:
https://chromium.googlesource.com/external/webrtc/+/b4c82474be64b815141284e37...
==========

[danilchap, 2016-03-17 12:15:26]

Committed patchset #1 (id:1) manually as
b4c82474be64b815141284e37a188b998dc45fb5 (presubmit successful).

[commit-bot: I haz the power, 2016-03-17 12:15:27]

Description was changed from

==========
Added function for parsing single rtcp packet in tests.

BUG=webrtc:5260
R=pbos@webrtc.org

Committed:
https://chromium.googlesource.com/external/webrtc/+/b4c82474be64b815141284e37...
==========

to

==========
Added function for parsing single rtcp packet in tests.

BUG=webrtc:5260
R=pbos@webrtc.org

Committed: https://crrev.com/b4c82474be64b815141284e37a188b998dc45fb5
Cr-Commit-Position: refs/heads/master@{#12033}
==========

[commit-bot: I haz the power, 2016-03-17 12:15:28]

Patchset 1 (id:??) landed as
https://crrev.com/b4c82474be64b815141284e37a188b998dc45fb5
Cr-Commit-Position: refs/heads/master@{#12033}