Remove unused AlarmTimer, OneShotAlarmTimer, RepeatingAlarmTimer

All AlarmTimer variants but SimpleAlarmTimer have no user in Chromium
and ChromeOS repositories, and base::Timer is being refactored.
As a preparation for the refactoring, this CL removes unused
OneShotAlarmTimer and RepeatingAlarmTimer, and merge SimpleAlarmTimer
into the AlarmTimer.

Bug: 850247
Change-Id: I78b7b7fea7a20edb51e3ad708d2fccceae85bd9d
Reviewed-on: https://chromium-review.googlesource.com/1095201
Reviewed-by: Chirantan Ekbote <chirantan@chromium.org>
Commit-Queue: Taiju Tsuiki <tzik@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#566303}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 3b99c6385b5bd9895856812fe94dd2125a6459ae
3 files changed