Revert of Use TaskScheduler instead of blocking pool in content_hash_fetcher.cc.

Revert of Use TaskScheduler instead of blocking pool in content_hash_fetcher.cc. (patchset #4 id:60001 of https://codereview.chromium.org/2672623006/ )

Reason for revert:
Causing flakyness https://crbug.com/702300

Original issue's description:
> Use TaskScheduler instead of blocking pool in content_hash_fetcher.cc.
> 
> The blocking pool is being deprecated in favor of TaskScheduler.
> 
> BUG=667892
> R=finnur@chromium.org
> 
> Review-Url: https://codereview.chromium.org/2672623006
> Cr-Commit-Position: refs/heads/master@{#451473}
> Committed: https://chromium.googlesource.com/chromium/src/+/8a07a9568d954e17452e678852692838a613f3c1

TBR=rdevlin.cronin@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=667892
Review-Url: https://codereview.chromium.org/2787453003
Cr-Commit-Position: refs/heads/master@{#460381}
Committed: https://chromium.googlesource.com/chromium/src/+/3056319cc7510415c98bb98e2529dfbcb1d973c4

[fdoray, 2017-03-29 13:46:30]

The CQ bit was checked by fdoray@chromium.org

[fdoray, 2017-03-29 13:46:30]

Created Revert of Use TaskScheduler instead of blocking pool in
content_hash_fetcher.cc.

[commit-bot: I haz the power, 2017-03-29 13:46:43]

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, 2017-03-29 14:33:51]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1490795190551960, "parent_rev":
"124254af04fd234fffa434b8b4380f5056528e3b", "commit_rev":
"3056319cc7510415c98bb98e2529dfbcb1d973c4"}

[commit-bot: I haz the power, 2017-03-29 14:34:38]

Description was changed from

==========
Revert of Use TaskScheduler instead of blocking pool in content_hash_fetcher.cc.
(patchset #4 id:60001 of https://codereview.chromium.org/2672623006/ )

Reason for revert:
Causing flakyness https://crbug.com/702300

Original issue's description:
> Use TaskScheduler instead of blocking pool in content_hash_fetcher.cc.
> 
> The blocking pool is being deprecated in favor of TaskScheduler.
> 
> BUG=667892
> R=finnur@chromium.org
> 
> Review-Url: https://codereview.chromium.org/2672623006
> Cr-Commit-Position: refs/heads/master@{#451473}
> Committed:
https://chromium.googlesource.com/chromium/src/+/8a07a9568d954e17452e67885269...

TBR=rdevlin.cronin@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=667892
==========

to

==========
Revert of Use TaskScheduler instead of blocking pool in content_hash_fetcher.cc.
(patchset #4 id:60001 of https://codereview.chromium.org/2672623006/ )

Reason for revert:
Causing flakyness https://crbug.com/702300

Original issue's description:
> Use TaskScheduler instead of blocking pool in content_hash_fetcher.cc.
> 
> The blocking pool is being deprecated in favor of TaskScheduler.
> 
> BUG=667892
> R=finnur@chromium.org
> 
> Review-Url: https://codereview.chromium.org/2672623006
> Cr-Commit-Position: refs/heads/master@{#451473}
> Committed:
https://chromium.googlesource.com/chromium/src/+/8a07a9568d954e17452e67885269...

TBR=rdevlin.cronin@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=667892

Review-Url: https://codereview.chromium.org/2787453003
Cr-Commit-Position: refs/heads/master@{#460381}
Committed:
https://chromium.googlesource.com/chromium/src/+/3056319cc7510415c98bb98e2529...
==========

[commit-bot: I haz the power, 2017-03-29 14:34:38]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/3056319cc7510415c98bb98e2529...