Revert of Use FileDescriptorWatcher in AlarmTimer. (patchset #2 id:20001 of https://codereview.chromium.org/2398753003/ )

Reason for revert:
This CL is causing a memory leak in the unit tests:

https://build.chromium.org/p/chromium.memory/builders/Linux%20Chromium%20OS%20ASan%20LSan%20Tests%20%281%29/builds/16728

failures:
AlarmTimerTest.RetainNonRepeatIsRunning
AlarmTimerTest.MessageLoopShutdown
AlarmTimerTest.NonRepeatIsRunning
AlarmTimerTest.RetainRepeatIsRunning

Sample report:
Direct leak of 152 byte(s) in 1 object(s) allocated from:
    #0 0xab8ebb in operator new(unsigned long) (/b/swarm_slave/w/irlnnUGq/out/Release/components_unittests+0xab8ebb)
    #1 0x9eba8fd in MakeUnique<base::FileDescriptorWatcher::Controller::Watcher, base::WeakPtr<base::FileDescriptorWatcher::Controller>, base::MessageLoopForIO::Mode &, int &> base/memory/ptr_util.h:56:29
    #2 0x9eba8fd in base::FileDescriptorWatcher::Controller::Controller(base::MessageLoopForIO::Mode, int, base::Callback<void (), (base::internal::CopyMode)1, (base::internal::RepeatMode)1> const&) base/files/file_descriptor_watcher_posix.cc:159
    #3 0x9ebb293 in base::FileDescriptorWatcher::WatchReadable(int, base::Callback<void (), (base::internal::CopyMode)1, (base::internal::RepeatMode)1> const&) base/files/file_descriptor_watcher_posix.cc:198:25
    #4 0xe0016a3 in timers::AlarmTimer::Reset() components/timers/alarm_timer_chromeos.cc:103:25
    #5 0x515b488 in timers::AlarmTimerTest_RetainRepeatIsRunning_Test::TestBody() components/timers/alarm_timer_unittest.cc:310:9

Original issue's description:
> Use FileDescriptorWatcher in AlarmTimer.
>
> FileDescriptorWatcher is a new API that replaces
> MessageLoopForIO::WatchFileDescriptor.
>
> This CL also gets rid of the base::Thread created in the anonymous
> namespace of alarm_timer_chromeos.cc. The FileDescriptorWatcher
> API is supported by every TaskScheduler thread. Very soon, most
> tasks in Chrome will run in TaskScheduler. Therefore, there is no
> reason to create a base::Thread to allow AlarmTimer to be used from
> threads that don't support the FileDescriptorWatcher API.
>
> BUG=645114
>
> Committed: https://crrev.com/8e17d7e9031b7e2e58473fe66a399943051357f0
> Cr-Commit-Position: refs/heads/master@{#423617}

TBR=chirantan@chromium.org,fdoray@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=645114

Review-Url: https://codereview.chromium.org/2394333002
Cr-Original-Commit-Position: refs/heads/master@{#423685}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 7a53efb2ae89077b62b7cc5ccbb11bf01246d20b
3 files changed