Initialize PeerConnection members in declaration order and destroy them in reverse order.

Initialize PeerConnection members in declaration order and destroy them in reverse order.

BUG=webrtc:7658
Review-Url: https://codereview.webrtc.org/2882803002
Cr-Commit-Position: refs/heads/master@{#18130}
Committed: https://chromium.googlesource.com/external/webrtc/+/338602596cab95d90137409ab1d9ca462c859156

[terelius, 2017-05-12 22:56:14]

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

[commit-bot: I haz the power, 2017-05-12 22:56:20]

Dry run: CQ is trying da patch.

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

[terelius, 2017-05-12 22:57:17]

terelius@webrtc.org changed reviewers:
+ deadbeef@webrtc.org, nisse@webrtc.org, tommi@webrtc.org

[Taylor Brandstetter, 2017-05-12 23:24:48]

lgtm

[commit-bot: I haz the power, 2017-05-12 23:27:33]

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

[commit-bot: I haz the power, 2017-05-12 23:27:33]

Dry run: This issue passed the CQ dry run.

[tommi, 2017-05-13 06:34:35]

The CQ bit was checked by tommi@webrtc.org

[tommi, 2017-05-13 06:34:36]

lgtm

[commit-bot: I haz the power, 2017-05-13 06:34:51]

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, 2017-05-13 06:37:18]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1494657275787570, "parent_rev":
"d0ffa8615d9f0aa5d5e3d17e5cab6ebdddc21846", "commit_rev":
"338602596cab95d90137409ab1d9ca462c859156"}

[commit-bot: I haz the power, 2017-05-13 06:37:22]

Description was changed from

==========
Initialize PeerConnection members in declaration order and destroy them in
reverse order.

BUG=webrtc:7658
==========

to

==========
Initialize PeerConnection members in declaration order and destroy them in
reverse order.

BUG=webrtc:7658

Review-Url: https://codereview.webrtc.org/2882803002
Cr-Commit-Position: refs/heads/master@{#18130}
Committed:
https://chromium.googlesource.com/external/webrtc/+/338602596cab95d90137409ab...
==========

[commit-bot: I haz the power, 2017-05-13 06:37:23]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/external/webrtc/+/338602596cab95d90137409ab...

[nisse-webrtc, 2017-05-15 06:44:42]

On 2017/05/13 06:37:23, commit-bot: I haz the power wrote:
> Committed patchset #1 (id:1) as
>
https://chromium.googlesource.com/external/webrtc/+/338602596cab95d90137409ab...

It seems a bit brittle if we must put declarations in the correct order, *and*
be very careful about the order things are teared down in the PeerConnection
destructor.

It would be nicer if we could just rely on the members being destructed in the
order implied by their declarations. It seems the tricky part is that the
objects that need to be destroyed last, port_allocator_ and call_, must be
destroyed on the worker thread. So to get that to be done automatically, we'd
need some helper class with a unique_ptr and a thread to use for destruction.

For the other objects, it looks a bit simpler, one would need to have streams'
Stop() method and the stat collector's WaitForPendingRequest be implied by
destruction.

|event_log_| already is set only on construction, so could be marked const. It
would be nice if we could do that for |stats_| and |stats_collector_| too, by
that depends on above reorganization of the destructor.