Revert of StartTimestamp generated randomly in RtpSender constructor

Revert of StartTimestamp generated randomly in RtpSender constructor (patchset #4 id:60001 of https://codereview.webrtc.org/2241193002/ )

Reason for revert:
Breaks downstream code.

Original issue's description:
> StartTimestamp generated randomly in RtpSender constructor
> instead of not-randomly at SetSendingState(true)
> Renamed to timestamp_offset_ to better match meaning of the variable.
>
> R=asapersson@webrtc.org, terelius@webrtc.org
>
> Committed: https://crrev.com/4466782ae43e1b1125a55ee7e18abd10dd37cede
> Cr-Commit-Position: refs/heads/master@{#13796}

TBR=asapersson@webrtc.org,terelius@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Committed: https://crrev.com/86c96948e340cf8b879bddb0c7293f3b5ad4dad4
Cr-Commit-Position: refs/heads/master@{#13798}

[danilchap, 2016-08-17 15:12:09]

The CQ bit was checked by danilchap@webrtc.org

[danilchap, 2016-08-17 15:12:10]

Created Revert of StartTimestamp generated randomly in RtpSender constructor

[commit-bot: I haz the power, 2016-08-17 15:12:18]

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, 2016-08-17 15:12:27]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-08-17 15:12:33]

Description was changed from

==========
Revert of StartTimestamp generated randomly in RtpSender constructor (patchset
#4 id:60001 of https://codereview.webrtc.org/2241193002/ )

Reason for revert:
Breaks downstream code.

Original issue's description:
> StartTimestamp generated randomly in RtpSender constructor
> instead of not-randomly at SetSendingState(true)
> Renamed to timestamp_offset_ to better match meaning of the variable.
> 
> R=asapersson@webrtc.org, terelius@webrtc.org
> 
> Committed: https://crrev.com/4466782ae43e1b1125a55ee7e18abd10dd37cede
> Cr-Commit-Position: refs/heads/master@{#13796}

TBR=asapersson@webrtc.org,terelius@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
==========

to

==========
Revert of StartTimestamp generated randomly in RtpSender constructor (patchset
#4 id:60001 of https://codereview.webrtc.org/2241193002/ )

Reason for revert:
Breaks downstream code.

Original issue's description:
> StartTimestamp generated randomly in RtpSender constructor
> instead of not-randomly at SetSendingState(true)
> Renamed to timestamp_offset_ to better match meaning of the variable.
>
> R=asapersson@webrtc.org, terelius@webrtc.org
>
> Committed: https://crrev.com/4466782ae43e1b1125a55ee7e18abd10dd37cede
> Cr-Commit-Position: refs/heads/master@{#13796}

TBR=asapersson@webrtc.org,terelius@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Committed: https://crrev.com/86c96948e340cf8b879bddb0c7293f3b5ad4dad4
Cr-Commit-Position: refs/heads/master@{#13798}
==========

[commit-bot: I haz the power, 2016-08-17 15:12:34]

Patchset 1 (id:??) landed as
https://crrev.com/86c96948e340cf8b879bddb0c7293f3b5ad4dad4
Cr-Commit-Position: refs/heads/master@{#13798}

[danilchap, 2016-08-18 09:01:38]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.webrtc.org/2257083002/ by danilchap@webrtc.org.

The reason for reverting is: Reland: downstream code expectation about
rtp_sender timestamp adjusted..