Introduce helpers to RtpSender to propagate RtpPacketToSend.

Introduce helpers to RtpSender to propagate RtpPacketToSend.
The helpers intended to replace and deprecate BuildRtpHeader when
RtpSenderAudio/RtpSenderVideo will be updated to pass RtpPacket class
instead of raw buffer for sending.

BUG=webrtc:5261
R=sprang@webrtc.org

Committed: https://chromium.googlesource.com/external/webrtc/+/5e57b17283f78dbc0f72815746bdda6d9a92b8f2

[danilchap, 2016-09-02 13:00:52]

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

[danilchap, 2016-09-02 13:00:52]

Sample usage (and follow-up CL:
https://codereview.webrtc.org/2292883002/diff/1/webrtc/modules/rtp_rtcp/sourc...)

[sprang_webrtc, 2016-09-02 13:56:44]

lgtm

https://codereview.webrtc.org/2303283002/diff/1/webrtc/modules/rtp_rtcp/sourc...
File webrtc/modules/rtp_rtcp/source/rtp_sender_unittest.cc (right):

https://codereview.webrtc.org/2303283002/diff/1/webrtc/modules/rtp_rtcp/sourc...
webrtc/modules/rtp_rtcp/source/rtp_sender_unittest.cc:465: // Parse the padding
packet and verify it's timestamp.
nit: s/it's/its

[commit-bot: I haz the power, 2016-09-02 17:16:11]

Description was changed from

==========
Introduce helpers to RtpSender to propagate RtpPacketToSend.
The helpers intended to replace and deprecate BuildRtpHeader when
RtpSenderAudio/RtpSenderVideo will be updated to pass RtpPacket class
instead of raw buffer for sending.

BUG=webrtc:5261
==========

to

==========
Introduce helpers to RtpSender to propagate RtpPacketToSend.
The helpers intended to replace and deprecate BuildRtpHeader when
RtpSenderAudio/RtpSenderVideo will be updated to pass RtpPacket class
instead of raw buffer for sending.

BUG=webrtc:5261
R=sprang@webrtc.org

Committed: https://crrev.com/5e57b17283f78dbc0f72815746bdda6d9a92b8f2
Cr-Commit-Position: refs/heads/master@{#14051}
==========

[commit-bot: I haz the power, 2016-09-02 17:16:12]

Patchset 2 (id:??) landed as
https://crrev.com/5e57b17283f78dbc0f72815746bdda6d9a92b8f2
Cr-Commit-Position: refs/heads/master@{#14051}

[danilchap, 2016-09-02 17:16:15]

Description was changed from

==========
Introduce helpers to RtpSender to propagate RtpPacketToSend.
The helpers intended to replace and deprecate BuildRtpHeader when
RtpSenderAudio/RtpSenderVideo will be updated to pass RtpPacket class
instead of raw buffer for sending.

BUG=webrtc:5261
R=sprang@webrtc.org

Committed: https://crrev.com/5e57b17283f78dbc0f72815746bdda6d9a92b8f2
Cr-Commit-Position: refs/heads/master@{#14051}
==========

to

==========
Introduce helpers to RtpSender to propagate RtpPacketToSend.
The helpers intended to replace and deprecate BuildRtpHeader when
RtpSenderAudio/RtpSenderVideo will be updated to pass RtpPacket class
instead of raw buffer for sending.

BUG=webrtc:5261
R=sprang@webrtc.org

Committed:
https://chromium.googlesource.com/external/webrtc/+/5e57b17283f78dbc0f7281574...
==========

[danilchap, 2016-09-02 17:16:16]

Committed patchset #2 (id:20001) manually as
5e57b17283f78dbc0f72815746bdda6d9a92b8f2 (presubmit successful).