The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/1e87b9aeba21ab5108409067f045861e0620a6a3

commit 1e87b9aeba21ab5108409067f045861e0620a6a3
Author: François Doray <fdoray@chromium.org>
Date: Fri Aug 24 21:37:58 2018

Revert "[Base] Use background mode for ThreadPriority::BACKGROUND threads (behind feature) (reland)."

This reverts commit d88c3ec18b44afe5a8f4a5b147e7e15dead47426.

Reason for revert: PlatformThreadTest.SetCurrentThreadPriorityWithThreadModeBackground is Flaky:
https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=base_unittests&tests=SetCurrentThreadPriorityWithThreadModeBackground

Original change's description:
> [Base] Use background mode for ThreadPriority::BACKGROUND threads (behind feature) (reland).
>
> Relanding a CL that was reverted because of a variable that was
> unused in non-DCHECK builds and caused a compile failure.
> Original CL: Reviewed-on: https://chromium-review.googlesource.com/1171482
>
> This CL adds a feature to use THREAD_MODE_BACKGROUND_BEGIN instead of
> THREAD_PRIORITY_LOWEST for ThreadPriority::BACKGROUND threads. This
> lowers the disk and network I/O priority of the thread in addition to
> the CPU scheduling priority. MSDN recommends using this setting for
> threads that perform background work.
> https://docs.microsoft.com/en-us/windows/desktop/api/processthreadsapi/nf-processthreadsapi-setthreadpriority
>
> TBR=gab@chromium.org
>
> Bug: 872820
> Change-Id: I212fb77bb035088595b4944ce145a74d333c38eb
> Reviewed-on: https://chromium-review.googlesource.com/1185529
> Commit-Queue: François Doray <fdoray@chromium.org>
> Commit-Queue: Gabriel Charette <gab@chromium.org>
> Reviewed-by: Gabriel Charette <gab@chromium.org>
> Reviewed-by: François Doray <fdoray@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#585272}

TBR=gab@chromium.org,fdoray@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 872820,  877628 
Change-Id: I6cf6625fc1f01106e8fff1e206a6a256f3a6160a
Reviewed-on: https://chromium-review.googlesource.com/1188644
Commit-Queue: François Doray <fdoray@chromium.org>
Reviewed-by: François Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585999}
[modify] https://crrev.com/1e87b9aeba21ab5108409067f045861e0620a6a3/base/BUILD.gn
[modify] https://crrev.com/1e87b9aeba21ab5108409067f045861e0620a6a3/base/threading/platform_thread_unittest.cc
[modify] https://crrev.com/1e87b9aeba21ab5108409067f045861e0620a6a3/base/threading/platform_thread_win.cc
[delete] https://crrev.com/3a41274e80c4b8b81733cd8b9c0f7e0bf6ae4b13/base/threading/platform_thread_win.h