RTCStatsCollector: Get track IDs from senders/receivers instead of streams

RTCStatsCollector: Get track IDs from senders/receivers instead of
streams.

When addTrack/removeTrack is used instead of addStream/removeStream
we an end up with tracks that are not contained within any local or
remote stream.

If all track IDs are not mapped when we produce RTCRTPStreamStats
we'll hit a DCHECK.

BUG=chromium:741638
Review-Url: https://codereview.webrtc.org/2978793002
Cr-Commit-Position: refs/heads/master@{#18991}
Committed: https://chromium.googlesource.com/external/webrtc/+/7b0c6fa2743ee79f080723aed2d9bea3a8325313

[hbos, 2017-07-12 18:49:30]

Description was changed from

==========
RTCStatsCollector: Get track IDs from senders/receivers instead of streams

BUG=
==========

to

==========
RTCStatsCollector: Get track IDs from senders/receivers instead of
streams.

When addTrack/removeTrack is used instead of addStream/removeStream
we an end up with tracks that are not contained within any local or
remote stream.

If all track IDs are not mapped when we produce RTCRTPStreamStats
we'll hit a DCHECK.

BUG=chromium:741638
==========

[hbos, 2017-07-12 18:49:30]

hbos@webrtc.org changed reviewers:
+ deadbeef@webrtc.org

[hbos, 2017-07-12 18:50:24]

The CQ bit was checked by hbos@webrtc.org to run a CQ dry run

[commit-bot: I haz the power, 2017-07-12 18:50:32]

Dry run: CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.webrtc.org/...

[hbos, 2017-07-12 18:56:54]

PTAL deadbeef.

I've verified that this fixes the crash of the referenced bug.
There's no easy unittest to add to cover this, the unittest uses mocks so how
tracks are added to the peerconnection is N/A in rtcstatscollector_unittest.cc.
The integrationtest on the other hand (rtcstats_integrationtest.cc) uses a
PeerConnectionTestWrapper to set up a real call and it's not parameterized
whether it should use addStream or addTrack, it's likely it uses
getLocalStreams() somewhere - I don't want to experiment with changing this
class for the sake of covering this one, though it probably should be updated to
use addTrack when we deprecate addStream.

I'd like to land this as-is (or possibly with a TODO about testing with both
addTrack and addStream). I'm OOO for a few days now and this bug has already hit
canary for those who use web experimental platform features and addTrack.

[commit-bot: I haz the power, 2017-07-12 20:13:43]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-07-12 20:13:44]

Dry run: This issue passed the CQ dry run.

[Taylor Brandstetter, 2017-07-12 23:18:52]

lgtm. I'm not worried about the test since this code is on life support anyway
(I assume)

[Taylor Brandstetter, 2017-07-12 23:19:04]

The CQ bit was checked by deadbeef@webrtc.org

[commit-bot: I haz the power, 2017-07-12 23:19:13]

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, 2017-07-12 23:22:34]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1499901544333290, "parent_rev":
"23173a372b3cec70fe890f50ad0d01d8d2fe6d35", "commit_rev":
"7b0c6fa2743ee79f080723aed2d9bea3a8325313"}

[commit-bot: I haz the power, 2017-07-12 23:22:38]

Description was changed from

==========
RTCStatsCollector: Get track IDs from senders/receivers instead of
streams.

When addTrack/removeTrack is used instead of addStream/removeStream
we an end up with tracks that are not contained within any local or
remote stream.

If all track IDs are not mapped when we produce RTCRTPStreamStats
we'll hit a DCHECK.

BUG=chromium:741638
==========

to

==========
RTCStatsCollector: Get track IDs from senders/receivers instead of
streams.

When addTrack/removeTrack is used instead of addStream/removeStream
we an end up with tracks that are not contained within any local or
remote stream.

If all track IDs are not mapped when we produce RTCRTPStreamStats
we'll hit a DCHECK.

BUG=chromium:741638

Review-Url: https://codereview.webrtc.org/2978793002
Cr-Commit-Position: refs/heads/master@{#18991}
Committed:
https://chromium.googlesource.com/external/webrtc/+/7b0c6fa2743ee79f080723aed...
==========

[commit-bot: I haz the power, 2017-07-12 23:22:39]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/external/webrtc/+/7b0c6fa2743ee79f080723aed...