Revert of Use TaskScheduler instead of WorkerPool in nss_cert_database.cc.

Revert of Use TaskScheduler instead of WorkerPool in nss_cert_database.cc. (patchset #4 id:60001 of https://codereview.chromium.org/2603173002/ )

Reason for revert:
Using TaskScheduler with NSS is not safe until TaskScheduler supports dynamically growing its thread pool.

Original issue's description:
> Use TaskScheduler instead of WorkerPool in nss_cert_database.cc.
> 
> Also, remove NSSCertDatabase::SetSlowTaskRunnerForTest(). This method
> was used to run slow NSSCertDatabase tasks synchronously in tests. This
> is no longer useful since tasks posted through the post_task.h API within
> the scope of a ScopedTaskScheduler run synchronously.
> 
> The following traits are used to post tasks to TaskScheduler:
> 
> Priority: Inherited (default)
>   The priority is inherited from the calling context (i.e. TaskTraits
>   are initialized with the priority of the current task).
> 
> Shutdown behavior: CONTINUE_ON_SHUTDOWN
>   Tasks posted with this mode which have not started executing before
>   shutdown is initiated will never run. Tasks with this mode running at
>   shutdown will be ignored (the worker will not be joined).
> 
>   Note: Tasks that were previously posted to base::WorkerPool should
>   use this shutdown behavior because this is how base::WorkerPool
>   handles all its tasks.
> 
> May Block:
>   Tasks posted with MayBlock() may block. This includes but is not
>   limited to tasks that wait on synchronous file I/O operations:
>   read or write a file from disk, interact with a pipe or a socket,
>   rename or delete a file, enumerate files in a directory, etc. This
>   trait isn't required for the mere use of locks.
> 
> BUG=659191
> 
> Review-Url: https://codereview.chromium.org/2603173002
> Cr-Commit-Position: refs/heads/master@{#448059}
> Committed: https://chromium.googlesource.com/chromium/src/+/982a31fe2c2dc31014dfaf373c6e5da6f094dcc4

TBR=rsleevi@chromium.org,stevenjb@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=659191
Review-Url: https://codereview.chromium.org/2722733002
Cr-Commit-Position: refs/heads/master@{#453475}
Committed: https://chromium.googlesource.com/chromium/src/+/37b8327d48552831f10e5d136f80cdac085abbc7

[fdoray, 2017-02-28 01:26:23]

The CQ bit was checked by fdoray@chromium.org

[fdoray, 2017-02-28 01:26:23]

Created Revert of Use TaskScheduler instead of WorkerPool in
nss_cert_database.cc.

[commit-bot: I haz the power, 2017-02-28 01:27:09]

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, 2017-02-28 01:31:00]

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

[commit-bot: I haz the power, 2017-02-28 01:31:01]

Try jobs failed on following builders:
  ios-device-xcode-clang on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-device-xcode-...)
  ios-simulator on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-simulator/bui...)
  ios-simulator-xcode-clang on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-simulator-xco...)
  mac_chromium_compile_dbg_ng on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_comp...)
  mac_chromium_rel_ng on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_rel_...)

[fdoray, 2017-02-28 01:36:07]

The CQ bit was checked by fdoray@chromium.org

[commit-bot: I haz the power, 2017-02-28 01:36:46]

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, 2017-02-28 02:42:20]

CQ is committing da patch.

Bot data: {"patchset_id": 230001, "attempt_start_ts": 1488245767765680,
"parent_rev": "2a3860be32817ca9b59c6051b3a194879b310cf9", "commit_rev":
"37b8327d48552831f10e5d136f80cdac085abbc7"}

[commit-bot: I haz the power, 2017-02-28 02:43:00]

Description was changed from

==========
Revert of Use TaskScheduler instead of WorkerPool in nss_cert_database.cc.
(patchset #4 id:60001 of https://codereview.chromium.org/2603173002/ )

Reason for revert:
Using TaskScheduler with NSS is not safe until TaskScheduler supports
dynamically growing its thread pool.

Original issue's description:
> Use TaskScheduler instead of WorkerPool in nss_cert_database.cc.
> 
> Also, remove NSSCertDatabase::SetSlowTaskRunnerForTest(). This method
> was used to run slow NSSCertDatabase tasks synchronously in tests. This
> is no longer useful since tasks posted through the post_task.h API within
> the scope of a ScopedTaskScheduler run synchronously.
> 
> The following traits are used to post tasks to TaskScheduler:
> 
> Priority: Inherited (default)
>   The priority is inherited from the calling context (i.e. TaskTraits
>   are initialized with the priority of the current task).
> 
> Shutdown behavior: CONTINUE_ON_SHUTDOWN
>   Tasks posted with this mode which have not started executing before
>   shutdown is initiated will never run. Tasks with this mode running at
>   shutdown will be ignored (the worker will not be joined).
> 
>   Note: Tasks that were previously posted to base::WorkerPool should
>   use this shutdown behavior because this is how base::WorkerPool
>   handles all its tasks.
> 
> May Block:
>   Tasks posted with MayBlock() may block. This includes but is not
>   limited to tasks that wait on synchronous file I/O operations:
>   read or write a file from disk, interact with a pipe or a socket,
>   rename or delete a file, enumerate files in a directory, etc. This
>   trait isn't required for the mere use of locks.
> 
> BUG=659191
> 
> Review-Url: https://codereview.chromium.org/2603173002
> Cr-Commit-Position: refs/heads/master@{#448059}
> Committed:
https://chromium.googlesource.com/chromium/src/+/982a31fe2c2dc31014dfaf373c6e...

TBR=rsleevi@chromium.org,stevenjb@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=659191
==========

to

==========
Revert of Use TaskScheduler instead of WorkerPool in nss_cert_database.cc.
(patchset #4 id:60001 of https://codereview.chromium.org/2603173002/ )

Reason for revert:
Using TaskScheduler with NSS is not safe until TaskScheduler supports
dynamically growing its thread pool.

Original issue's description:
> Use TaskScheduler instead of WorkerPool in nss_cert_database.cc.
> 
> Also, remove NSSCertDatabase::SetSlowTaskRunnerForTest(). This method
> was used to run slow NSSCertDatabase tasks synchronously in tests. This
> is no longer useful since tasks posted through the post_task.h API within
> the scope of a ScopedTaskScheduler run synchronously.
> 
> The following traits are used to post tasks to TaskScheduler:
> 
> Priority: Inherited (default)
>   The priority is inherited from the calling context (i.e. TaskTraits
>   are initialized with the priority of the current task).
> 
> Shutdown behavior: CONTINUE_ON_SHUTDOWN
>   Tasks posted with this mode which have not started executing before
>   shutdown is initiated will never run. Tasks with this mode running at
>   shutdown will be ignored (the worker will not be joined).
> 
>   Note: Tasks that were previously posted to base::WorkerPool should
>   use this shutdown behavior because this is how base::WorkerPool
>   handles all its tasks.
> 
> May Block:
>   Tasks posted with MayBlock() may block. This includes but is not
>   limited to tasks that wait on synchronous file I/O operations:
>   read or write a file from disk, interact with a pipe or a socket,
>   rename or delete a file, enumerate files in a directory, etc. This
>   trait isn't required for the mere use of locks.
> 
> BUG=659191
> 
> Review-Url: https://codereview.chromium.org/2603173002
> Cr-Commit-Position: refs/heads/master@{#448059}
> Committed:
https://chromium.googlesource.com/chromium/src/+/982a31fe2c2dc31014dfaf373c6e...

TBR=rsleevi@chromium.org,stevenjb@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=659191

Review-Url: https://codereview.chromium.org/2722733002
Cr-Commit-Position: refs/heads/master@{#453475}
Committed:
https://chromium.googlesource.com/chromium/src/+/37b8327d48552831f10e5d136f80...
==========

[commit-bot: I haz the power, 2017-02-28 02:43:01]

Committed patchset #2 (id:230001) as
https://chromium.googlesource.com/chromium/src/+/37b8327d48552831f10e5d136f80...