Revert of RedirectNonUINonIOBrowserThreads to TaskScheduler by default on trunk.

Revert of RedirectNonUINonIOBrowserThreads to TaskScheduler by default on trunk. (patchset #3 id:40001 of https://codereview.chromium.org/2690183002/ )

Reason for revert:
Breaks some DBUS code that requests for a message loop

Original issue's description:
> RedirectNonUINonIOBrowserThreads to TaskScheduler by default on trunk.
> 
> The addition of AssertWaitAllowed in BrowserMainLoop::ShutdownThreadsAndCleanUp()
> is required because joining is a "wait" operation. It wasn't required
> before because PlatformThread::Join (platform_thread_posix.cc) actually still
> does AssertIOAllowed() instead of AssertWaitAllowed() for legacy reasons
> (and I/O is allowed in shutdown already). But this CL enables the redirection
> which uses a WaitableEvent to mimic thread join (ref. BrowserThreadImpl::StopRedirectionOfThreadID(): 
> waiting on the exact same set of tasks it did prior to redirection).
> 
> BUG=653916
> 
> Review-Url: https://codereview.chromium.org/2690183002
> Cr-Commit-Position: refs/heads/master@{#461481}
> Committed: https://chromium.googlesource.com/chromium/src/+/b6d0c9a06ab573af760763fcd7ecf76ae2c87695

TBR=jam@chromium.org,rkaplow@chromium.org,gab@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=653916, 707986
Review-Url: https://codereview.chromium.org/2791933004
Cr-Commit-Position: refs/heads/master@{#461588}
Committed: https://chromium.googlesource.com/chromium/src/+/f07732ec0e39ad7e9f1ad279f2624dbdf261803d

[robliao, 2017-04-04 00:29:52]

Created Revert of RedirectNonUINonIOBrowserThreads to TaskScheduler by default
on trunk.

[robliao, 2017-04-04 00:30:03]

Description was changed from

==========
Revert of RedirectNonUINonIOBrowserThreads to TaskScheduler by default on trunk.
(patchset #3 id:40001 of https://codereview.chromium.org/2690183002/ )

Reason for revert:
Breaks some DBUS code that requests for a message loop

Original issue's description:
> RedirectNonUINonIOBrowserThreads to TaskScheduler by default on trunk.
> 
> The addition of AssertWaitAllowed in
BrowserMainLoop::ShutdownThreadsAndCleanUp()
> is required because joining is a "wait" operation. It wasn't required
> before because PlatformThread::Join (platform_thread_posix.cc) actually still
> does AssertIOAllowed() instead of AssertWaitAllowed() for legacy reasons
> (and I/O is allowed in shutdown already). But this CL enables the redirection
> which uses a WaitableEvent to mimic thread join (ref.
BrowserThreadImpl::StopRedirectionOfThreadID(): 
> waiting on the exact same set of tasks it did prior to redirection).
> 
> BUG=653916
> 
> Review-Url: https://codereview.chromium.org/2690183002
> Cr-Commit-Position: refs/heads/master@{#461481}
> Committed:
https://chromium.googlesource.com/chromium/src/+/b6d0c9a06ab573af760763fcd7ec...

TBR=jam@chromium.org,rkaplow@chromium.org,gab@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=653916
==========

to

==========
Revert of RedirectNonUINonIOBrowserThreads to TaskScheduler by default on trunk.
(patchset #3 id:40001 of https://codereview.chromium.org/2690183002/ )

Reason for revert:
Breaks some DBUS code that requests for a message loop

Original issue's description:
> RedirectNonUINonIOBrowserThreads to TaskScheduler by default on trunk.
> 
> The addition of AssertWaitAllowed in
BrowserMainLoop::ShutdownThreadsAndCleanUp()
> is required because joining is a "wait" operation. It wasn't required
> before because PlatformThread::Join (platform_thread_posix.cc) actually still
> does AssertIOAllowed() instead of AssertWaitAllowed() for legacy reasons
> (and I/O is allowed in shutdown already). But this CL enables the redirection
> which uses a WaitableEvent to mimic thread join (ref.
BrowserThreadImpl::StopRedirectionOfThreadID(): 
> waiting on the exact same set of tasks it did prior to redirection).
> 
> BUG=653916
> 
> Review-Url: https://codereview.chromium.org/2690183002
> Cr-Commit-Position: refs/heads/master@{#461481}
> Committed:
https://chromium.googlesource.com/chromium/src/+/b6d0c9a06ab573af760763fcd7ec...

TBR=jam@chromium.org,rkaplow@chromium.org,gab@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=653916, 707986
==========

[robliao, 2017-04-04 00:30:11]

The CQ bit was checked by robliao@chromium.org

[commit-bot: I haz the power, 2017-04-04 00:30:47]

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, 2017-04-04 00:33:37]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1491265811789260, "parent_rev":
"fb5c907d801f5fb0d6542c14f29c5749ae78abc7", "commit_rev":
"f07732ec0e39ad7e9f1ad279f2624dbdf261803d"}

[commit-bot: I haz the power, 2017-04-04 00:35:10]

Description was changed from

==========
Revert of RedirectNonUINonIOBrowserThreads to TaskScheduler by default on trunk.
(patchset #3 id:40001 of https://codereview.chromium.org/2690183002/ )

Reason for revert:
Breaks some DBUS code that requests for a message loop

Original issue's description:
> RedirectNonUINonIOBrowserThreads to TaskScheduler by default on trunk.
> 
> The addition of AssertWaitAllowed in
BrowserMainLoop::ShutdownThreadsAndCleanUp()
> is required because joining is a "wait" operation. It wasn't required
> before because PlatformThread::Join (platform_thread_posix.cc) actually still
> does AssertIOAllowed() instead of AssertWaitAllowed() for legacy reasons
> (and I/O is allowed in shutdown already). But this CL enables the redirection
> which uses a WaitableEvent to mimic thread join (ref.
BrowserThreadImpl::StopRedirectionOfThreadID(): 
> waiting on the exact same set of tasks it did prior to redirection).
> 
> BUG=653916
> 
> Review-Url: https://codereview.chromium.org/2690183002
> Cr-Commit-Position: refs/heads/master@{#461481}
> Committed:
https://chromium.googlesource.com/chromium/src/+/b6d0c9a06ab573af760763fcd7ec...

TBR=jam@chromium.org,rkaplow@chromium.org,gab@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=653916, 707986
==========

to

==========
Revert of RedirectNonUINonIOBrowserThreads to TaskScheduler by default on trunk.
(patchset #3 id:40001 of https://codereview.chromium.org/2690183002/ )

Reason for revert:
Breaks some DBUS code that requests for a message loop

Original issue's description:
> RedirectNonUINonIOBrowserThreads to TaskScheduler by default on trunk.
> 
> The addition of AssertWaitAllowed in
BrowserMainLoop::ShutdownThreadsAndCleanUp()
> is required because joining is a "wait" operation. It wasn't required
> before because PlatformThread::Join (platform_thread_posix.cc) actually still
> does AssertIOAllowed() instead of AssertWaitAllowed() for legacy reasons
> (and I/O is allowed in shutdown already). But this CL enables the redirection
> which uses a WaitableEvent to mimic thread join (ref.
BrowserThreadImpl::StopRedirectionOfThreadID(): 
> waiting on the exact same set of tasks it did prior to redirection).
> 
> BUG=653916
> 
> Review-Url: https://codereview.chromium.org/2690183002
> Cr-Commit-Position: refs/heads/master@{#461481}
> Committed:
https://chromium.googlesource.com/chromium/src/+/b6d0c9a06ab573af760763fcd7ec...

TBR=jam@chromium.org,rkaplow@chromium.org,gab@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=653916, 707986

Review-Url: https://codereview.chromium.org/2791933004
Cr-Commit-Position: refs/heads/master@{#461588}
Committed:
https://chromium.googlesource.com/chromium/src/+/f07732ec0e39ad7e9f1ad279f262...
==========

[commit-bot: I haz the power, 2017-04-04 00:35:10]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/f07732ec0e39ad7e9f1ad279f262...