Reland of Make RtcEventLogImpl to use a TaskQueue instead of a helper-thread

Reland of Make RtcEventLogImpl to use a TaskQueue instead of a helper-thread (patchset #1 id:1 of https://codereview.webrtc.org/3010143002/ )

Reason for revert:
I will fix and reland.

Original issue's description:
> Revert of Make RtcEventLogImpl to use a TaskQueue instead of a helper-thread (patchset #18 id:340001 of https://codereview.webrtc.org/3007473002/ )
> 
> Reason for revert:
> Breaks google3 project.
> 
> Original issue's description:
> > Make RtcEventLogImpl to use a TaskQueue instead of a helper-thread
> > 
> > Make RtcEventLogImpl to use a TaskQueue instead of a helper-thread. This will eventually allow us to run multiple log sessions on a single task-queue.
> > 
> > BUG=webrtc:8142, webrtc:8143, webrtc:8145
> > 
> > Review-Url: https://codereview.webrtc.org/3007473002
> > Cr-Commit-Position: refs/heads/master@{#19666}
> > Committed: https://chromium.googlesource.com/external/webrtc/+/f33cee7534f0469330b6b7aa57f84eec4b082598
> 
> TBR=terelius@webrtc.org,nisse@webrtc.org,eladalon@webrtc.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=webrtc:8142, webrtc:8143, webrtc:8145
> 
> Review-Url: https://codereview.webrtc.org/3010143002
> Cr-Commit-Position: refs/heads/master@{#19672}
> Committed: https://chromium.googlesource.com/external/webrtc/+/3eac8002db8fdf5124026d5377a1f3ec1d16bb0d

TBR=terelius@webrtc.org,nisse@webrtc.org,charujain@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:8142, webrtc:8143, webrtc:8145
Review-Url: https://codereview.webrtc.org/3005153002
Cr-Commit-Position: refs/heads/master@{#19690}
Committed: https://chromium.googlesource.com/external/webrtc/+/d67cefbbeab0a092d1fa250c811c25733dced043

[eladalon, 2017-09-05 12:32:36]

Created Reland of Make RtcEventLogImpl to use a TaskQueue instead of a
helper-thread

[eladalon, 2017-09-05 13:04:31]

eladalon@webrtc.org changed reviewers:
+ kwiberg@webrtc.org
- charujain@webrtc.org

[eladalon, 2017-09-05 13:04:33]

I've made sure creation and destruction would happen on the same thread. PTAL.

https://codereview.webrtc.org/3005153002/diff/160001/webrtc/pc/peerconnection...
File webrtc/pc/peerconnectionfactory.cc (right):

https://codereview.webrtc.org/3005153002/diff/160001/webrtc/pc/peerconnection...
webrtc/pc/peerconnectionfactory.cc:263: std::unique_ptr<RtcEventLog> event_log =
There's a trade-off between Invoke()-ing twice (blocking function), which makes
for cleaner code, and doing two different things in (a renamed version of)
CreateCall_w, which is more efficient. Thoughts?

[terelius, 2017-09-05 14:28:14]

lgtm, but please have a PeerConnection OWNER review those changes.

[perkj_webrtc, 2017-09-05 15:07:42]

perkj@webrtc.org changed reviewers:
+ perkj@webrtc.org

[perkj_webrtc, 2017-09-05 15:07:42]

lgtm

[eladalon, 2017-09-05 15:14:49]

The CQ bit was checked by eladalon@webrtc.org

[eladalon, 2017-09-05 15:14:49]

The patchset sent to the CQ was uploaded after l-g-t-m from terelius@webrtc.org,
perkj@webrtc.org
Link to the patchset: https://codereview.webrtc.org/3005153002/#ps200001 (title:
".")

[commit-bot: I haz the power, 2017-09-05 15:14:58]

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, 2017-09-05 15:15:03]

CQ is committing da patch.

Bot data: {"patchset_id": 200001, "attempt_start_ts": 1504624489160150,
"parent_rev": "0b510a994692df0137b39d38427e7c7311bdad27", "commit_rev":
"d67cefbbeab0a092d1fa250c811c25733dced043"}

[commit-bot: I haz the power, 2017-09-05 15:15:08]

Description was changed from

==========
Reland of Make RtcEventLogImpl to use a TaskQueue instead of a helper-thread
(patchset #1 id:1 of https://codereview.webrtc.org/3010143002/ )

Reason for revert:
I will fix and reland.

Original issue's description:
> Revert of Make RtcEventLogImpl to use a TaskQueue instead of a helper-thread
(patchset #18 id:340001 of https://codereview.webrtc.org/3007473002/ )
> 
> Reason for revert:
> Breaks google3 project.
> 
> Original issue's description:
> > Make RtcEventLogImpl to use a TaskQueue instead of a helper-thread
> > 
> > Make RtcEventLogImpl to use a TaskQueue instead of a helper-thread. This
will eventually allow us to run multiple log sessions on a single task-queue.
> > 
> > BUG=webrtc:8142, webrtc:8143, webrtc:8145
> > 
> > Review-Url: https://codereview.webrtc.org/3007473002
> > Cr-Commit-Position: refs/heads/master@{#19666}
> > Committed:
https://chromium.googlesource.com/external/webrtc/+/f33cee7534f0469330b6b7aa5...
> 
> TBR=terelius@webrtc.org,nisse@webrtc.org,eladalon@webrtc.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=webrtc:8142, webrtc:8143, webrtc:8145
> 
> Review-Url: https://codereview.webrtc.org/3010143002
> Cr-Commit-Position: refs/heads/master@{#19672}
> Committed:
https://chromium.googlesource.com/external/webrtc/+/3eac8002db8fdf5124026d537...

TBR=terelius@webrtc.org,nisse@webrtc.org,charujain@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:8142, webrtc:8143, webrtc:8145
==========

to

==========
Reland of Make RtcEventLogImpl to use a TaskQueue instead of a helper-thread
(patchset #1 id:1 of https://codereview.webrtc.org/3010143002/ )

Reason for revert:
I will fix and reland.

Original issue's description:
> Revert of Make RtcEventLogImpl to use a TaskQueue instead of a helper-thread
(patchset #18 id:340001 of https://codereview.webrtc.org/3007473002/ )
> 
> Reason for revert:
> Breaks google3 project.
> 
> Original issue's description:
> > Make RtcEventLogImpl to use a TaskQueue instead of a helper-thread
> > 
> > Make RtcEventLogImpl to use a TaskQueue instead of a helper-thread. This
will eventually allow us to run multiple log sessions on a single task-queue.
> > 
> > BUG=webrtc:8142, webrtc:8143, webrtc:8145
> > 
> > Review-Url: https://codereview.webrtc.org/3007473002
> > Cr-Commit-Position: refs/heads/master@{#19666}
> > Committed:
https://chromium.googlesource.com/external/webrtc/+/f33cee7534f0469330b6b7aa5...
> 
> TBR=terelius@webrtc.org,nisse@webrtc.org,eladalon@webrtc.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=webrtc:8142, webrtc:8143, webrtc:8145
> 
> Review-Url: https://codereview.webrtc.org/3010143002
> Cr-Commit-Position: refs/heads/master@{#19672}
> Committed:
https://chromium.googlesource.com/external/webrtc/+/3eac8002db8fdf5124026d537...

TBR=terelius@webrtc.org,nisse@webrtc.org,charujain@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:8142, webrtc:8143, webrtc:8145

Review-Url: https://codereview.webrtc.org/3005153002
Cr-Commit-Position: refs/heads/master@{#19690}
Committed:
https://chromium.googlesource.com/external/webrtc/+/d67cefbbeab0a092d1fa250c8...
==========

[commit-bot: I haz the power, 2017-09-05 15:15:09]

Committed patchset #4 (id:200001) as
https://chromium.googlesource.com/external/webrtc/+/d67cefbbeab0a092d1fa250c8...

[eladalon, 2017-09-05 15:33:41]

A revert of this CL (patchset #4 id:200001) has been created in
https://codereview.webrtc.org/3007193002/ by eladalon@webrtc.org.

The reason for reverting is: Landed without CQ, which was unintended..