Revert of Disallow posting tasks to SequencedWorkerPools by default. (patchset #25 id:480001 of https://codereview.chromium.org/2445763002/ )
Reason for revert:
chrome --mash crashing.
Original issue's description:
> Disallow posting tasks to SequencedWorkerPools by default.
>
> We have observed crash reports in which SequencedWorkerPool workers
> were active while redirection to TaskScheduler was enabled. This can
> happen if a task is posted to a SequencedWorkerPool before redirection
> to TaskScheduler is enabled. With this CL, DumpWithoutCrashing() is
> called if a task is posted to a SequencedWorkerPool too early. This
> will help us find offending call sites.
>
> A commented DCHECK is also added to find offending call sites. It
> will be uncommented in a separate CL to avoid a revert of this CL
> in case it fails on the waterfall.
>
> BUG=622400
>
> Committed: https://crrev.com/4606ada249a240e115a08a7c66409e8fdd457ea1
> Committed: https://crrev.com/8fd22217395d50b6704109c7f1d4deff59f9a109
> Cr-Original-Commit-Position: refs/heads/master@{#432913}
> Cr-Commit-Position: refs/heads/master@{#433237}
TBR=gab@chromium.org,brettw@chromium.org,fdoray@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=622400
Review-Url: https://codereview.chromium.org/2519543002
Cr-Commit-Position: refs/heads/master@{#433267}
12 files changed
