Revert of Refactor signaling in RWP

Revert of Refactor signaling in RWP (patchset #9 id:180001 of https://codereview.chromium.org/1666283002/ )

Reason for revert:
Broke the thread_times.tough_scrolling_cases test (verified with a local revert):

https://build.chromium.org/p/chromium.perf/builders/Linux%20Perf%20%281%29/builds/10247

Original issue's description:
> Refactor signaling in RWP
>
> A previous patch had moved RasterWorkerPool to make heavy use of
> broadcast in order to simplify logic a bit. It turns out that broadcast
> is not ideal in performance critical situations, as it increases lock
> contention (see
> https://code.google.com/p/chromium/codesearch#chromium/src/base/synchronization/condition_variable.h&l=34).
>
> This change removes all uses of broadcast other than in Shutdown, where
> performance is less of a concern and we actually need all threads to
> wake up.
>
> To achieve this, we need to re-factor RWP to use:
>  - N foreground threads
>  - 1 background thread
> rather than N threads which may be able to run foreground/background tasks.
>
> In order to ensure that we don't overload the system, this change
> introduces a limiting system where the background priority thread can only
> run tasks if no other threads are doing so.
>
> BUG=
> CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

TBR=reveman@chromium.org,sievers@chromium.org,avi.rohit@gmail.com,ericrk@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=

Committed: https://crrev.com/a1c7eb7f23d0a275d223144a1cffbf3714d8982f
Cr-Commit-Position: refs/heads/master@{#375195}

[Sami, 2016-02-12 17:12:45]

Created Revert of Refactor signaling in RWP

[commit-bot: I haz the power, 2016-02-12 17:13:14]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1690023005/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1690023005/1

[commit-bot: I haz the power, 2016-02-12 17:14:18]

Description was changed from

==========
Revert of Refactor signaling in RWP (patchset #9 id:180001 of
https://codereview.chromium.org/1666283002/ )

Reason for revert:
Broke the thread_times.tough_scrolling_cases test (verified with a local
revert):

https://build.chromium.org/p/chromium.perf/builders/Linux%20Perf%20%281%29/bu...

Original issue's description:
> Refactor signaling in RWP
> 
> A previous patch had moved RasterWorkerPool to make heavy use of
> broadcast in order to simplify logic a bit. It turns out that broadcast
> is not ideal in performance critical situations, as it increases lock
> contention (see
>
https://code.google.com/p/chromium/codesearch#chromium/src/base/synchronizati...).
> 
> This change removes all uses of broadcast other than in Shutdown, where
> performance is less of a concern and we actually need all threads to
> wake up.
> 
> To achieve this, we need to re-factor RWP to use:
>  - N foreground threads
>  - 1 background thread
> rather than N threads which may be able to run foreground/background tasks.
> 
> In order to ensure that we don't overload the system, this change
> introduces a limiting system where the background priority thread can only
> run tasks if no other threads are doing so.
> 
> BUG=
> CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

TBR=reveman@chromium.org,sievers@chromium.org,avi.rohit@gmail.com,ericrk@chro...
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=
==========

to

==========
Revert of Refactor signaling in RWP (patchset #9 id:180001 of
https://codereview.chromium.org/1666283002/ )

Reason for revert:
Broke the thread_times.tough_scrolling_cases test (verified with a local
revert):

https://build.chromium.org/p/chromium.perf/builders/Linux%20Perf%20%281%29/bu...

Original issue's description:
> Refactor signaling in RWP
> 
> A previous patch had moved RasterWorkerPool to make heavy use of
> broadcast in order to simplify logic a bit. It turns out that broadcast
> is not ideal in performance critical situations, as it increases lock
> contention (see
>
https://code.google.com/p/chromium/codesearch#chromium/src/base/synchronizati...).
> 
> This change removes all uses of broadcast other than in Shutdown, where
> performance is less of a concern and we actually need all threads to
> wake up.
> 
> To achieve this, we need to re-factor RWP to use:
>  - N foreground threads
>  - 1 background thread
> rather than N threads which may be able to run foreground/background tasks.
> 
> In order to ensure that we don't overload the system, this change
> introduces a limiting system where the background priority thread can only
> run tasks if no other threads are doing so.
> 
> BUG=
> CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

TBR=reveman@chromium.org,sievers@chromium.org,avi.rohit@gmail.com,ericrk@chro...
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=
==========

[commit-bot: I haz the power, 2016-02-12 17:14:18]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-02-16 22:43:32]

Description was changed from

==========
Revert of Refactor signaling in RWP (patchset #9 id:180001 of
https://codereview.chromium.org/1666283002/ )

Reason for revert:
Broke the thread_times.tough_scrolling_cases test (verified with a local
revert):

https://build.chromium.org/p/chromium.perf/builders/Linux%20Perf%20%281%29/bu...

Original issue's description:
> Refactor signaling in RWP
> 
> A previous patch had moved RasterWorkerPool to make heavy use of
> broadcast in order to simplify logic a bit. It turns out that broadcast
> is not ideal in performance critical situations, as it increases lock
> contention (see
>
https://code.google.com/p/chromium/codesearch#chromium/src/base/synchronizati...).
> 
> This change removes all uses of broadcast other than in Shutdown, where
> performance is less of a concern and we actually need all threads to
> wake up.
> 
> To achieve this, we need to re-factor RWP to use:
>  - N foreground threads
>  - 1 background thread
> rather than N threads which may be able to run foreground/background tasks.
> 
> In order to ensure that we don't overload the system, this change
> introduces a limiting system where the background priority thread can only
> run tasks if no other threads are doing so.
> 
> BUG=
> CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

TBR=reveman@chromium.org,sievers@chromium.org,avi.rohit@gmail.com,ericrk@chro...
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=
==========

to

==========
Revert of Refactor signaling in RWP (patchset #9 id:180001 of
https://codereview.chromium.org/1666283002/ )

Reason for revert:
Broke the thread_times.tough_scrolling_cases test (verified with a local
revert):

https://build.chromium.org/p/chromium.perf/builders/Linux%20Perf%20%281%29/bu...

Original issue's description:
> Refactor signaling in RWP
>
> A previous patch had moved RasterWorkerPool to make heavy use of
> broadcast in order to simplify logic a bit. It turns out that broadcast
> is not ideal in performance critical situations, as it increases lock
> contention (see
>
https://code.google.com/p/chromium/codesearch#chromium/src/base/synchronizati...).
>
> This change removes all uses of broadcast other than in Shutdown, where
> performance is less of a concern and we actually need all threads to
> wake up.
>
> To achieve this, we need to re-factor RWP to use:
>  - N foreground threads
>  - 1 background thread
> rather than N threads which may be able to run foreground/background tasks.
>
> In order to ensure that we don't overload the system, this change
> introduces a limiting system where the background priority thread can only
> run tasks if no other threads are doing so.
>
> BUG=
> CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

TBR=reveman@chromium.org,sievers@chromium.org,avi.rohit@gmail.com,ericrk@chro...
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=

Committed: https://crrev.com/a1c7eb7f23d0a275d223144a1cffbf3714d8982f
Cr-Commit-Position: refs/heads/master@{#375195}
==========

[commit-bot: I haz the power, 2016-02-16 22:43:33]

Patchset 1 (id:??) landed as
https://crrev.com/a1c7eb7f23d0a275d223144a1cffbf3714d8982f
Cr-Commit-Position: refs/heads/master@{#375195}