Revert of Remove unused blocking pool methods from web::WebThread.

Revert of Remove unused blocking pool methods from web::WebThread. (patchset #3 id:40001 of https://codereview.chromium.org/2906753004/ )

Reason for revert:
This is blocking revert of https://codereview.chromium.org/2881873002.

Original issue's description:
> Remove unused blocking pool methods from web::WebThread.
> 
> These methods are unused and deprecated in favor of TaskScheduler.
> 
> BUG=667892
> 
> Review-Url: https://codereview.chromium.org/2906753004
> Cr-Commit-Position: refs/heads/master@{#475126}
> Committed: https://chromium.googlesource.com/chromium/src/+/c342fa0f3ef65dbb37db1df35c02ded2d989902e

TBR=eugenebut@chromium.org,gab@chromium.org,fdoray@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=667892
Review-Url: https://codereview.chromium.org/2915583002
Cr-Commit-Position: refs/heads/master@{#475510}
Committed: https://chromium.googlesource.com/chromium/src/+/11d8154eb4cc10a04f18b0b7a254995765aff569

[sdefresne, 2017-05-30 10:24:11]

The CQ bit was checked by sdefresne@chromium.org

[sdefresne, 2017-05-30 10:24:11]

Created Revert of Remove unused blocking pool methods from web::WebThread.

[commit-bot: I haz the power, 2017-05-30 10:24:24]

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, 2017-05-30 10:33:18]

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

[commit-bot: I haz the power, 2017-05-30 10:33:19]

Try jobs failed on following builders:
  ios-device on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-device/builds...)

[sdefresne, 2017-05-30 12:53:09]

The CQ bit was checked by sdefresne@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-05-30 12:53:21]

Dry run: CQ is trying da patch.

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

[sdefresne, 2017-05-30 12:54:39]

The CQ bit was checked by sdefresne@chromium.org

[commit-bot: I haz the power, 2017-05-30 12:54:42]

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, 2017-05-30 13:22:26]

CQ is committing da patch.

Bot data: {"patchset_id": 70001, "attempt_start_ts": 1496148879125020,
"parent_rev": "09d12909d7aea834c41bfcc455b15e30d27154e0", "commit_rev":
"11d8154eb4cc10a04f18b0b7a254995765aff569"}

[commit-bot: I haz the power, 2017-05-30 13:22:33]

Description was changed from

==========
Revert of Remove unused blocking pool methods from web::WebThread. (patchset #3
id:40001 of https://codereview.chromium.org/2906753004/ )

Reason for revert:
This is blocking revert of https://codereview.chromium.org/2881873002.

Original issue's description:
> Remove unused blocking pool methods from web::WebThread.
> 
> These methods are unused and deprecated in favor of TaskScheduler.
> 
> BUG=667892
> 
> Review-Url: https://codereview.chromium.org/2906753004
> Cr-Commit-Position: refs/heads/master@{#475126}
> Committed:
https://chromium.googlesource.com/chromium/src/+/c342fa0f3ef65dbb37db1df35c02...

TBR=eugenebut@chromium.org,gab@chromium.org,fdoray@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=667892
==========

to

==========
Revert of Remove unused blocking pool methods from web::WebThread. (patchset #3
id:40001 of https://codereview.chromium.org/2906753004/ )

Reason for revert:
This is blocking revert of https://codereview.chromium.org/2881873002.

Original issue's description:
> Remove unused blocking pool methods from web::WebThread.
> 
> These methods are unused and deprecated in favor of TaskScheduler.
> 
> BUG=667892
> 
> Review-Url: https://codereview.chromium.org/2906753004
> Cr-Commit-Position: refs/heads/master@{#475126}
> Committed:
https://chromium.googlesource.com/chromium/src/+/c342fa0f3ef65dbb37db1df35c02...

TBR=eugenebut@chromium.org,gab@chromium.org,fdoray@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=667892

Review-Url: https://codereview.chromium.org/2915583002
Cr-Commit-Position: refs/heads/master@{#475510}
Committed:
https://chromium.googlesource.com/chromium/src/+/11d8154eb4cc10a04f18b0b7a254...
==========

[commit-bot: I haz the power, 2017-05-30 13:22:35]

Committed patchset #2 (id:70001) as
https://chromium.googlesource.com/chromium/src/+/11d8154eb4cc10a04f18b0b7a254...

[Eugene But (OOO till 7-30), 2017-05-30 14:34:58]

lgtm