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

Review-Url: https://codereview.chromium.org/2398753003
Cr-Commit-Position: refs/heads/master@{#423617}


CrOS-Libchrome-Original-Commit: 8e17d7e9031b7e2e58473fe66a399943051357f0
3 files changed
tree: 96cb43c651bff7ba71701c7ab9d2d19454647c8c
  1. base/
  2. build/
  3. components/
  4. dbus/
  5. device/
  6. ipc/
  7. mojo/
  8. testing/
  9. third_party/
  10. ui/