Revert of Delete SignalThread class.

Revert of Delete SignalThread class. (patchset #20 id:380001 of https://codereview.webrtc.org/2915253002/ )

Reason for revert:
Seems to be causing new crashes, possibly because of changes to the "Destroy(false)" behavior. Will re-land after investigating these crashes more and addressing the root cause.

Original issue's description:
> Delete SignalThread class.
> 
> Rewrite AsyncResolver to use PlatformThread directly, not
> SignalThread, and update includes of peerconnection client to not
> depend on signalthread.h.
> 
> BUG=webrtc:6424, webrtc:7723
> 
> Review-Url: https://codereview.webrtc.org/2915253002
> Cr-Commit-Position: refs/heads/master@{#18833}
> Committed: https://chromium.googlesource.com/external/webrtc/+/bc8feda1db02b2a9b501e4aa43926ca7e861b638

TBR=tommi@webrtc.org,kwiberg@webrtc.org,nisse@webrtc.org
NOPRESUBMIT=true
NOTRY=true
BUG=webrtc:6424, webrtc:7723
Review-Url: https://codereview.webrtc.org/2979733002
Cr-Commit-Position: refs/heads/master@{#18980}
Committed: https://chromium.googlesource.com/external/webrtc/+/8290ddfbce0ecd3d178c1bc280007dd796819538

[Taylor Brandstetter, 2017-07-11 18:01:47]

The CQ bit was checked by deadbeef@webrtc.org

[Taylor Brandstetter, 2017-07-11 18:01:49]

Created Revert of Delete SignalThread class.

[commit-bot: I haz the power, 2017-07-11 18:01:52]

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, 2017-07-11 18:03:21]

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

[commit-bot: I haz the power, 2017-07-11 18:03:22]

Try jobs failed on following builders:
  ios32_sim_ios9_dbg on master.tryserver.webrtc (JOB_FAILED,
http://build.chromium.org/p/tryserver.webrtc/builders/ios32_sim_ios9_dbg/buil...)
  ios64_sim_ios10_dbg on master.tryserver.webrtc (JOB_FAILED,
http://build.chromium.org/p/tryserver.webrtc/builders/ios64_sim_ios10_dbg/bui...)
  ios_arm64_dbg on master.tryserver.webrtc (JOB_FAILED,
http://build.chromium.org/p/tryserver.webrtc/builders/ios_arm64_dbg/builds/21914)

[Taylor Brandstetter, 2017-07-11 19:35:43]

The CQ bit was checked by deadbeef@webrtc.org

[commit-bot: I haz the power, 2017-07-11 19:35:53]

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, 2017-07-11 19:38:21]

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

[commit-bot: I haz the power, 2017-07-11 19:38:22]

Try jobs failed on following builders:
  linux_arm64_rel on master.tryserver.webrtc (JOB_FAILED,
http://build.chromium.org/p/tryserver.webrtc/builders/linux_arm64_rel/builds/...)

[Taylor Brandstetter, 2017-07-11 21:32:37]

The CQ bit was checked by deadbeef@webrtc.org

[commit-bot: I haz the power, 2017-07-11 21:32:47]

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, 2017-07-11 21:36:55]

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

[commit-bot: I haz the power, 2017-07-11 21:36:56]

Try jobs failed on following builders:
  ios32_sim_ios9_dbg on master.tryserver.webrtc (JOB_FAILED,
http://build.chromium.org/p/tryserver.webrtc/builders/ios32_sim_ios9_dbg/buil...)
  ios64_sim_ios10_dbg on master.tryserver.webrtc (JOB_FAILED,
http://build.chromium.org/p/tryserver.webrtc/builders/ios64_sim_ios10_dbg/bui...)

[Taylor Brandstetter, 2017-07-11 22:39:46]

The CQ bit was checked by deadbeef@webrtc.org

[commit-bot: I haz the power, 2017-07-11 22:40:00]

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, 2017-07-11 22:45:26]

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

[commit-bot: I haz the power, 2017-07-11 22:45:27]

Try jobs failed on following builders:
  presubmit on master.tryserver.webrtc (JOB_FAILED,
http://build.chromium.org/p/tryserver.webrtc/builders/presubmit/builds/19171)

[Taylor Brandstetter, 2017-07-11 23:55:49]

Description was changed from

==========
Revert of Delete SignalThread class. (patchset #20 id:380001 of
https://codereview.webrtc.org/2915253002/ )

Reason for revert:
Seems to be causing new crashes, possibly because of changes to the
"Destroy(false)" behavior. Will re-land after investigating these crashes more
and addressing the root cause.

Original issue's description:
> Delete SignalThread class.
> 
> Rewrite AsyncResolver to use PlatformThread directly, not
> SignalThread, and update includes of peerconnection client to not
> depend on signalthread.h.
> 
> BUG=webrtc:6424,webrtc:7723
> 
> Review-Url: https://codereview.webrtc.org/2915253002
> Cr-Commit-Position: refs/heads/master@{#18833}
> Committed:
https://chromium.googlesource.com/external/webrtc/+/bc8feda1db02b2a9b501e4aa4...

TBR=tommi@webrtc.org,kwiberg@webrtc.org,nisse@webrtc.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=webrtc:6424,webrtc:7723
==========

to

==========
Revert of Delete SignalThread class. (patchset #20 id:380001 of
https://codereview.webrtc.org/2915253002/ )

Reason for revert:
Seems to be causing new crashes, possibly because of changes to the
"Destroy(false)" behavior. Will re-land after investigating these crashes more
and addressing the root cause.

Original issue's description:
> Delete SignalThread class.
> 
> Rewrite AsyncResolver to use PlatformThread directly, not
> SignalThread, and update includes of peerconnection client to not
> depend on signalthread.h.
> 
> BUG=webrtc:6424,webrtc:7723
> 
> Review-Url: https://codereview.webrtc.org/2915253002
> Cr-Commit-Position: refs/heads/master@{#18833}
> Committed:
https://chromium.googlesource.com/external/webrtc/+/bc8feda1db02b2a9b501e4aa4...

TBR=tommi@webrtc.org,kwiberg@webrtc.org,nisse@webrtc.org
NOPRESUBMIT=true
NOTRY=true
BUG=webrtc:6424,webrtc:7723
==========

[Taylor Brandstetter, 2017-07-11 23:55:53]

The CQ bit was checked by deadbeef@webrtc.org

[commit-bot: I haz the power, 2017-07-11 23:55:58]

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, 2017-07-11 23:56:05]

CQ is committing da patch.

Bot data: {"patchset_id": 290001, "attempt_start_ts": 1499817353722000,
"parent_rev": "1095ada7ad56fe29b7b2bbc560a8f6475a7978ce", "commit_rev":
"8290ddfbce0ecd3d178c1bc280007dd796819538"}

[commit-bot: I haz the power, 2017-07-11 23:56:13]

Description was changed from

==========
Revert of Delete SignalThread class. (patchset #20 id:380001 of
https://codereview.webrtc.org/2915253002/ )

Reason for revert:
Seems to be causing new crashes, possibly because of changes to the
"Destroy(false)" behavior. Will re-land after investigating these crashes more
and addressing the root cause.

Original issue's description:
> Delete SignalThread class.
> 
> Rewrite AsyncResolver to use PlatformThread directly, not
> SignalThread, and update includes of peerconnection client to not
> depend on signalthread.h.
> 
> BUG=webrtc:6424,webrtc:7723
> 
> Review-Url: https://codereview.webrtc.org/2915253002
> Cr-Commit-Position: refs/heads/master@{#18833}
> Committed:
https://chromium.googlesource.com/external/webrtc/+/bc8feda1db02b2a9b501e4aa4...

TBR=tommi@webrtc.org,kwiberg@webrtc.org,nisse@webrtc.org
NOPRESUBMIT=true
NOTRY=true
BUG=webrtc:6424,webrtc:7723
==========

to

==========
Revert of Delete SignalThread class. (patchset #20 id:380001 of
https://codereview.webrtc.org/2915253002/ )

Reason for revert:
Seems to be causing new crashes, possibly because of changes to the
"Destroy(false)" behavior. Will re-land after investigating these crashes more
and addressing the root cause.

Original issue's description:
> Delete SignalThread class.
> 
> Rewrite AsyncResolver to use PlatformThread directly, not
> SignalThread, and update includes of peerconnection client to not
> depend on signalthread.h.
> 
> BUG=webrtc:6424,webrtc:7723
> 
> Review-Url: https://codereview.webrtc.org/2915253002
> Cr-Commit-Position: refs/heads/master@{#18833}
> Committed:
https://chromium.googlesource.com/external/webrtc/+/bc8feda1db02b2a9b501e4aa4...

TBR=tommi@webrtc.org,kwiberg@webrtc.org,nisse@webrtc.org
NOPRESUBMIT=true
NOTRY=true
BUG=webrtc:6424,webrtc:7723

Review-Url: https://codereview.webrtc.org/2979733002
Cr-Commit-Position: refs/heads/master@{#18980}
Committed:
https://chromium.googlesource.com/external/webrtc/+/8290ddfbce0ecd3d178c1bc28...
==========

[commit-bot: I haz the power, 2017-07-11 23:56:14]

Committed patchset #4 (id:290001) as
https://chromium.googlesource.com/external/webrtc/+/8290ddfbce0ecd3d178c1bc28...