Remove IOObservers from MessageLoopForIO.

Remove IOObservers from MessageLoopForIO.

IOObservers aren't used anywhere.

We plan to redirect Tasks that run on the CACHE thread's
MessageLoopForIO to the new base/task_scheduler API. For
that, we have to replicate MessageLoopForIO's features in
base/task_scheduler. Removing features that aren't used
will make this easier.

BUG=553459
Committed: https://crrev.com/1d49f3c45fba20437ccaba796784deb3d5242e76
Cr-Commit-Position: refs/heads/master@{#392466}

[fdoray, 2016-05-03 19:56:05]

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

[commit-bot: I haz the power, 2016-05-03 19:56:29]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1950633002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1950633002/1

[fdoray, 2016-05-03 21:24:37]

Description was changed from

==========
Remove IO observers.

BUG=
==========

to

==========
Remove IOObservers from MessageLoopForIO.

IOObservers aren't used anywhere.

We plan to redirect Tasks that run on the CACHE thread's
MessageLoopForIO to the new base/task_scheduler API. For
that, we have to replicate MessageLoopForIO's features in
base/task_scheduler. Removing features that aren't used
will make this easier.

BUG=553459
==========

[commit-bot: I haz the power, 2016-05-03 21:26:15]

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

[commit-bot: I haz the power, 2016-05-03 21:26:16]

Dry run: This issue passed the CQ dry run.

[fdoray, 2016-05-03 21:28:43]

fdoray@chromium.org changed reviewers:
+ thestig@chromium.org

[fdoray, 2016-05-03 21:28:43]

thestig@: Can you review this CL? Thanks.

[fdoray, 2016-05-04 20:43:34]

fdoray@chromium.org changed reviewers:
+ thakis@chromium.org

[fdoray, 2016-05-04 20:43:34]

+thakis@: Can you review this CL? (thestig@ is OOO)

[fdoray, 2016-05-05 20:53:21]

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

[commit-bot: I haz the power, 2016-05-05 20:54:11]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1950633002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1950633002/20001

[commit-bot: I haz the power, 2016-05-06 00:33:02]

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

[commit-bot: I haz the power, 2016-05-06 00:33:03]

Dry run: This issue passed the CQ dry run.

[Lei Zhang, 2016-05-09 20:43:26]

lgtm

FWIW, this was added in r49188.

[fdoray, 2016-05-09 21:17:22]

The CQ bit was checked by fdoray@chromium.org

[commit-bot: I haz the power, 2016-05-09 21:18:14]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1950633002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1950633002/20001

[commit-bot: I haz the power, 2016-05-09 23:15:10]

Description was changed from

==========
Remove IOObservers from MessageLoopForIO.

IOObservers aren't used anywhere.

We plan to redirect Tasks that run on the CACHE thread's
MessageLoopForIO to the new base/task_scheduler API. For
that, we have to replicate MessageLoopForIO's features in
base/task_scheduler. Removing features that aren't used
will make this easier.

BUG=553459
==========

to

==========
Remove IOObservers from MessageLoopForIO.

IOObservers aren't used anywhere.

We plan to redirect Tasks that run on the CACHE thread's
MessageLoopForIO to the new base/task_scheduler API. For
that, we have to replicate MessageLoopForIO's features in
base/task_scheduler. Removing features that aren't used
will make this easier.

BUG=553459
==========

[commit-bot: I haz the power, 2016-05-09 23:15:11]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-05-09 23:16:41]

Description was changed from

==========
Remove IOObservers from MessageLoopForIO.

IOObservers aren't used anywhere.

We plan to redirect Tasks that run on the CACHE thread's
MessageLoopForIO to the new base/task_scheduler API. For
that, we have to replicate MessageLoopForIO's features in
base/task_scheduler. Removing features that aren't used
will make this easier.

BUG=553459
==========

to

==========
Remove IOObservers from MessageLoopForIO.

IOObservers aren't used anywhere.

We plan to redirect Tasks that run on the CACHE thread's
MessageLoopForIO to the new base/task_scheduler API. For
that, we have to replicate MessageLoopForIO's features in
base/task_scheduler. Removing features that aren't used
will make this easier.

BUG=553459

Committed: https://crrev.com/1d49f3c45fba20437ccaba796784deb3d5242e76
Cr-Commit-Position: refs/heads/master@{#392466}
==========

[commit-bot: I haz the power, 2016-05-09 23:16:43]

Patchset 2 (id:??) landed as
https://crrev.com/1d49f3c45fba20437ccaba796784deb3d5242e76
Cr-Commit-Position: refs/heads/master@{#392466}