Reland of TCRtpReceiver.getContributingSources() added.

Reland of TCRtpReceiver.getContributingSources() added. (patchset #1 id:1 of https://codereview.chromium.org/2813443003/ )

Reason for revert:
Reland. The dependent CL relanded, it was not the culprit of https://bugs.chromium.org/p/webrtc/issues/detail?id=7465.

Original issue's description:
> Revert of RTCRtpReceiver.getContributingSources() added. (patchset #8 id:160001 of https://codereview.chromium.org/2803693002/ )
> 
> Reason for revert:
> The dependent CL was reverted due to suspected of:
> https://bugs.chromium.org/p/webrtc/issues/detail?id=7465
> 
> Original issue's description:
> > RTCRtpReceiver.getContributingSources() added.
> > 
> > Adds RTCRtpReceiver.getContributingSources(),
> > https://w3c.github.io/webrtc-pc/#dom-rtcrtpreceiver-getcontributingsources,
> > and RTCRtpContributingSource,
> > https://w3c.github.io/webrtc-pc/#dom-rtcrtpcontributingsource,
> > behind flag "RuntimeEnabled=RTCRtpReceiver".
> > 
> > Contributing sources come in two flavors, SSRCs and CSRCs. This
> > interface represents both. For now we ignore SSRCs and only return
> > CSRCs. It was recently decided that SSRCs would be returned in a
> > separate method to distinguish between the two cases.
> > 
> > A LayoutTest is used to thoroughly test all blink functionality with
> > regards to CSRCs and the caching of contributing sources. This uses
> > mocking to update contributing sources in a predictable way.
> > 
> > The browsertest verifies that no contributing sources are used in a
> > normal peerconnection call. The multiple CSRCs case is currently not
> > possible to test in a browsertest so we rely on the LayoutTest (and
> > webrtc layer testing of contributing sources).
> > 
> > BUG=703122
> > 
> > Review-Url: https://codereview.chromium.org/2803693002
> > Cr-Commit-Position: refs/heads/master@{#463199}
> > Committed: https://chromium.googlesource.com/chromium/src/+/7a16f508ad712bc38ff72e979dd5155a4015c320
> 
> TBR=jochen@chromium.org,deadbeef@chromium.org,foolip@chromium.org,guidou@chromium.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=703122
> 
> Review-Url: https://codereview.chromium.org/2813443003
> Cr-Commit-Position: refs/heads/master@{#463226}
> Committed: https://chromium.googlesource.com/chromium/src/+/5209c4a740829998e6f5d78f0771d1fac8d20689

TBR=jochen@chromium.org,deadbeef@chromium.org,foolip@chromium.org,guidou@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=703122
Review-Url: https://codereview.chromium.org/2808113002
Cr-Commit-Position: refs/heads/master@{#463262}
Committed: https://chromium.googlesource.com/chromium/src/+/68d5bbddd28fd443982073c645aee01ed3f972de

[hbos_chromium, 2017-04-10 14:42:19]

The CQ bit was checked by hbos@chromium.org

[hbos_chromium, 2017-04-10 14:42:20]

Created Reland of TCRtpReceiver.getContributingSources() added.

[commit-bot: I haz the power, 2017-04-10 14:42:42]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-04-10 14:44:38]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1491835339670620, "parent_rev":
"30ec3ae2f047440cccf3e8a40ad14daf56ccc905", "commit_rev":
"68d5bbddd28fd443982073c645aee01ed3f972de"}

[commit-bot: I haz the power, 2017-04-10 14:45:27]

Description was changed from

==========
Reland of TCRtpReceiver.getContributingSources() added. (patchset #1 id:1 of
https://codereview.chromium.org/2813443003/ )

Reason for revert:
Reland. The dependent CL relanded, it was not the culprit of
https://bugs.chromium.org/p/webrtc/issues/detail?id=7465.

Original issue's description:
> Revert of RTCRtpReceiver.getContributingSources() added. (patchset #8
id:160001 of https://codereview.chromium.org/2803693002/ )
> 
> Reason for revert:
> The dependent CL was reverted due to suspected of:
> https://bugs.chromium.org/p/webrtc/issues/detail?id=7465
> 
> Original issue's description:
> > RTCRtpReceiver.getContributingSources() added.
> > 
> > Adds RTCRtpReceiver.getContributingSources(),
> > https://w3c.github.io/webrtc-pc/#dom-rtcrtpreceiver-getcontributingsources,
> > and RTCRtpContributingSource,
> > https://w3c.github.io/webrtc-pc/#dom-rtcrtpcontributingsource,
> > behind flag "RuntimeEnabled=RTCRtpReceiver".
> > 
> > Contributing sources come in two flavors, SSRCs and CSRCs. This
> > interface represents both. For now we ignore SSRCs and only return
> > CSRCs. It was recently decided that SSRCs would be returned in a
> > separate method to distinguish between the two cases.
> > 
> > A LayoutTest is used to thoroughly test all blink functionality with
> > regards to CSRCs and the caching of contributing sources. This uses
> > mocking to update contributing sources in a predictable way.
> > 
> > The browsertest verifies that no contributing sources are used in a
> > normal peerconnection call. The multiple CSRCs case is currently not
> > possible to test in a browsertest so we rely on the LayoutTest (and
> > webrtc layer testing of contributing sources).
> > 
> > BUG=703122
> > 
> > Review-Url: https://codereview.chromium.org/2803693002
> > Cr-Commit-Position: refs/heads/master@{#463199}
> > Committed:
https://chromium.googlesource.com/chromium/src/+/7a16f508ad712bc38ff72e979dd5...
> 
>
TBR=jochen@chromium.org,deadbeef@chromium.org,foolip@chromium.org,guidou@chro...
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=703122
> 
> Review-Url: https://codereview.chromium.org/2813443003
> Cr-Commit-Position: refs/heads/master@{#463226}
> Committed:
https://chromium.googlesource.com/chromium/src/+/5209c4a740829998e6f5d78f0771...

TBR=jochen@chromium.org,deadbeef@chromium.org,foolip@chromium.org,guidou@chro...
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=703122
==========

to

==========
Reland of TCRtpReceiver.getContributingSources() added. (patchset #1 id:1 of
https://codereview.chromium.org/2813443003/ )

Reason for revert:
Reland. The dependent CL relanded, it was not the culprit of
https://bugs.chromium.org/p/webrtc/issues/detail?id=7465.

Original issue's description:
> Revert of RTCRtpReceiver.getContributingSources() added. (patchset #8
id:160001 of https://codereview.chromium.org/2803693002/ )
> 
> Reason for revert:
> The dependent CL was reverted due to suspected of:
> https://bugs.chromium.org/p/webrtc/issues/detail?id=7465
> 
> Original issue's description:
> > RTCRtpReceiver.getContributingSources() added.
> > 
> > Adds RTCRtpReceiver.getContributingSources(),
> > https://w3c.github.io/webrtc-pc/#dom-rtcrtpreceiver-getcontributingsources,
> > and RTCRtpContributingSource,
> > https://w3c.github.io/webrtc-pc/#dom-rtcrtpcontributingsource,
> > behind flag "RuntimeEnabled=RTCRtpReceiver".
> > 
> > Contributing sources come in two flavors, SSRCs and CSRCs. This
> > interface represents both. For now we ignore SSRCs and only return
> > CSRCs. It was recently decided that SSRCs would be returned in a
> > separate method to distinguish between the two cases.
> > 
> > A LayoutTest is used to thoroughly test all blink functionality with
> > regards to CSRCs and the caching of contributing sources. This uses
> > mocking to update contributing sources in a predictable way.
> > 
> > The browsertest verifies that no contributing sources are used in a
> > normal peerconnection call. The multiple CSRCs case is currently not
> > possible to test in a browsertest so we rely on the LayoutTest (and
> > webrtc layer testing of contributing sources).
> > 
> > BUG=703122
> > 
> > Review-Url: https://codereview.chromium.org/2803693002
> > Cr-Commit-Position: refs/heads/master@{#463199}
> > Committed:
https://chromium.googlesource.com/chromium/src/+/7a16f508ad712bc38ff72e979dd5...
> 
>
TBR=jochen@chromium.org,deadbeef@chromium.org,foolip@chromium.org,guidou@chro...
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=703122
> 
> Review-Url: https://codereview.chromium.org/2813443003
> Cr-Commit-Position: refs/heads/master@{#463226}
> Committed:
https://chromium.googlesource.com/chromium/src/+/5209c4a740829998e6f5d78f0771...

TBR=jochen@chromium.org,deadbeef@chromium.org,foolip@chromium.org,guidou@chro...
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=703122

Review-Url: https://codereview.chromium.org/2808113002
Cr-Commit-Position: refs/heads/master@{#463262}
Committed:
https://chromium.googlesource.com/chromium/src/+/68d5bbddd28fd443982073c645ae...
==========

[commit-bot: I haz the power, 2017-04-10 14:45:29]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/68d5bbddd28fd443982073c645ae...