Revert of Revert "Allow SequencedTaskRunnerHandle::Get() while running unsequenced tasks."

Revert of Revert "Allow SequencedTaskRunnerHandle::Get() while running unsequenced tasks." (patchset #2 id:40001 of https://codereview.chromium.org/2177373005/ )

Reason for revert:
Actually oops forgot this wasn't supposed to land until this blocker is resolved : https://bugs.chromium.org/p/chromium/issues/detail?id=618043#c5

Original issue's description:
> Revert "Allow SequencedTaskRunnerHandle::Get() while running unsequenced tasks."
>
> This is effectively a manual revert of 5d315e4b4a7cdef34b0c1e863353d03a30781217.
>
> Per the outcome of the discussion on http://crbug.com/618043 and associated doc/chromium-dev discussion.
>
> BUG=618043
>
> Committed: https://crrev.com/41339c7ae8458dd500d1be0e9d4b8da6d8c4c33b
> Cr-Commit-Position: refs/heads/master@{#408440}

TBR=danakj@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=618043
Committed: https://crrev.com/33a2c419dbc05f970bc5de86ad7f3d3919a93bc2
Cr-Commit-Position: refs/heads/master@{#408448}

[gab, 2016-07-28 19:04:12]

The CQ bit was checked by gab@chromium.org

[gab, 2016-07-28 19:04:13]

Created Revert of Revert "Allow SequencedTaskRunnerHandle::Get() while running
unsequenced tasks."

[commit-bot: I haz the power, 2016-07-28 19:04:43]

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, 2016-07-28 19:05:51]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-07-28 19:09:57]

Description was changed from

==========
Revert of Revert "Allow SequencedTaskRunnerHandle::Get() while running
unsequenced tasks." (patchset #2 id:40001 of
https://codereview.chromium.org/2177373005/ )

Reason for revert:
Actually oops forgot this wasn't supposed to land until this blocker is resolved
: https://bugs.chromium.org/p/chromium/issues/detail?id=618043#c5

Original issue's description:
> Revert "Allow SequencedTaskRunnerHandle::Get() while running unsequenced
tasks."
> 
> This is effectively a manual revert of
5d315e4b4a7cdef34b0c1e863353d03a30781217.
> 
> Per the outcome of the discussion on http://crbug.com/618043 and associated
doc/chromium-dev discussion.
> 
> BUG=618043
> 
> Committed: https://crrev.com/41339c7ae8458dd500d1be0e9d4b8da6d8c4c33b
> Cr-Commit-Position: refs/heads/master@{#408440}

TBR=danakj@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=618043
==========

to

==========
Revert of Revert "Allow SequencedTaskRunnerHandle::Get() while running
unsequenced tasks." (patchset #2 id:40001 of
https://codereview.chromium.org/2177373005/ )

Reason for revert:
Actually oops forgot this wasn't supposed to land until this blocker is resolved
: https://bugs.chromium.org/p/chromium/issues/detail?id=618043#c5

Original issue's description:
> Revert "Allow SequencedTaskRunnerHandle::Get() while running unsequenced
tasks."
>
> This is effectively a manual revert of
5d315e4b4a7cdef34b0c1e863353d03a30781217.
>
> Per the outcome of the discussion on http://crbug.com/618043 and associated
doc/chromium-dev discussion.
>
> BUG=618043
>
> Committed: https://crrev.com/41339c7ae8458dd500d1be0e9d4b8da6d8c4c33b
> Cr-Commit-Position: refs/heads/master@{#408440}

TBR=danakj@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=618043

Committed: https://crrev.com/33a2c419dbc05f970bc5de86ad7f3d3919a93bc2
Cr-Commit-Position: refs/heads/master@{#408448}
==========

[commit-bot: I haz the power, 2016-07-28 19:09:58]

Patchset 1 (id:??) landed as
https://crrev.com/33a2c419dbc05f970bc5de86ad7f3d3919a93bc2
Cr-Commit-Position: refs/heads/master@{#408448}