Revert of [reland] Use TaskScheduler instead of SequencedWorkerPool in snapshot_cache.mm.

Revert of [reland] Use TaskScheduler instead of SequencedWorkerPool in snapshot_cache.mm. (patchset #8 id:140001 of https://codereview.chromium.org/2881873002/ )

Reason for revert:
This CL is incorrect. SnapshotCache is a singleton that is indirectly accessed by multiple unit tests (for example MainController unit tests).

CreateSequencedTaskRunnerWithTraits() returns an object that reference TaskScheduler::GetInstance(). This TaskScheduler object is detroyed between each test, thus we have a singleton object pointing to de-allocated memory.

SnapshotCache need to be changed to no longer be a singleton, this is tracked by https://bugs.chromium.org/p/chromium/issues/detail?id=727597.

Original issue's description:
> [reland] Use TaskScheduler instead of SequencedWorkerPool in snapshot_cache.mm.
> 
> Reland with fix in test.
> 
> SequencedWorkerPool is being deprecated in favor of TaskScheduler.
> 
> BUG=667892
> R=jif@chromium.org
> 
> Review-Url: https://codereview.chromium.org/2881873002
> Cr-Original-Commit-Position: refs/heads/master@{#472052}
> Committed: https://chromium.googlesource.com/chromium/src/+/aa5299ae23a57ca5dce00a11da3ac8e73849351f
> Review-Url: https://codereview.chromium.org/2881873002
> Cr-Commit-Position: refs/heads/master@{#475107}
> Committed: https://chromium.googlesource.com/chromium/src/+/a11be0d57a4e4f214588bbd6fab9398824802b7f

TBR=jif@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/2910183002
Cr-Commit-Position: refs/heads/master@{#475518}
Committed: https://chromium.googlesource.com/chromium/src/+/cf9d12f1999e34f40e9e3ee9e40829d4529cb55b

[sdefresne, 2017-05-30 10:15:05]

The CQ bit was checked by sdefresne@chromium.org

[sdefresne, 2017-05-30 10:15:06]

Created Revert of [reland] Use TaskScheduler instead of SequencedWorkerPool in
snapshot_cache.mm.

[commit-bot: I haz the power, 2017-05-30 10:15:17]

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 10:23:35]

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

[commit-bot: I haz the power, 2017-05-30 10:23:36]

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-...)

[sdefresne, 2017-05-30 12:54:14]

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

[commit-bot: I haz the power, 2017-05-30 12:54:23]

Dry run: 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 13:06:26]

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

[commit-bot: I haz the power, 2017-05-30 13:06:27]

Dry run: This issue passed the CQ dry run.

[sdefresne, 2017-05-30 13:57:06]

The CQ bit was checked by sdefresne@chromium.org

[commit-bot: I haz the power, 2017-05-30 13:57:22]

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 14:01:41]

CQ is committing da patch.

Bot data: {"patchset_id": 70001, "attempt_start_ts": 1496152626459150,
"parent_rev": "ce2464110221db485c26fd738c097c95c2269c13", "commit_rev":
"cf9d12f1999e34f40e9e3ee9e40829d4529cb55b"}

[commit-bot: I haz the power, 2017-05-30 14:01:49]

Description was changed from

==========
Revert of [reland] Use TaskScheduler instead of SequencedWorkerPool in
snapshot_cache.mm. (patchset #8 id:140001 of
https://codereview.chromium.org/2881873002/ )

Reason for revert:
This CL is incorrect. SnapshotCache is a singleton that is indirectly accessed
by multiple unit tests (for example MainController unit tests).

CreateSequencedTaskRunnerWithTraits() returns an object that reference
TaskScheduler::GetInstance(). This TaskScheduler object is detroyed between each
test, thus we have a singleton object pointing to de-allocated memory.

SnapshotCache need to be changed to no longer be a singleton, this is tracked by
https://bugs.chromium.org/p/chromium/issues/detail?id=727597.

Original issue's description:
> [reland] Use TaskScheduler instead of SequencedWorkerPool in
snapshot_cache.mm.
> 
> Reland with fix in test.
> 
> SequencedWorkerPool is being deprecated in favor of TaskScheduler.
> 
> BUG=667892
> R=jif@chromium.org
> 
> Review-Url: https://codereview.chromium.org/2881873002
> Cr-Original-Commit-Position: refs/heads/master@{#472052}
> Committed:
https://chromium.googlesource.com/chromium/src/+/aa5299ae23a57ca5dce00a11da3a...
> Review-Url: https://codereview.chromium.org/2881873002
> Cr-Commit-Position: refs/heads/master@{#475107}
> Committed:
https://chromium.googlesource.com/chromium/src/+/a11be0d57a4e4f214588bbd6fab9...

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

to

==========
Revert of [reland] Use TaskScheduler instead of SequencedWorkerPool in
snapshot_cache.mm. (patchset #8 id:140001 of
https://codereview.chromium.org/2881873002/ )

Reason for revert:
This CL is incorrect. SnapshotCache is a singleton that is indirectly accessed
by multiple unit tests (for example MainController unit tests).

CreateSequencedTaskRunnerWithTraits() returns an object that reference
TaskScheduler::GetInstance(). This TaskScheduler object is detroyed between each
test, thus we have a singleton object pointing to de-allocated memory.

SnapshotCache need to be changed to no longer be a singleton, this is tracked by
https://bugs.chromium.org/p/chromium/issues/detail?id=727597.

Original issue's description:
> [reland] Use TaskScheduler instead of SequencedWorkerPool in
snapshot_cache.mm.
> 
> Reland with fix in test.
> 
> SequencedWorkerPool is being deprecated in favor of TaskScheduler.
> 
> BUG=667892
> R=jif@chromium.org
> 
> Review-Url: https://codereview.chromium.org/2881873002
> Cr-Original-Commit-Position: refs/heads/master@{#472052}
> Committed:
https://chromium.googlesource.com/chromium/src/+/aa5299ae23a57ca5dce00a11da3a...
> Review-Url: https://codereview.chromium.org/2881873002
> Cr-Commit-Position: refs/heads/master@{#475107}
> Committed:
https://chromium.googlesource.com/chromium/src/+/a11be0d57a4e4f214588bbd6fab9...

TBR=jif@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/2910183002
Cr-Commit-Position: refs/heads/master@{#475518}
Committed:
https://chromium.googlesource.com/chromium/src/+/cf9d12f1999e34f40e9e3ee9e408...
==========

[commit-bot: I haz the power, 2017-05-30 14:01:50]

Committed patchset #2 (id:70001) as
https://chromium.googlesource.com/chromium/src/+/cf9d12f1999e34f40e9e3ee9e408...

[jif, 2017-05-31 14:45:27]

lgtm