Build base::AlarmTimer into libchrome.

Original Chrome OS commit message:

  crrev.com/26436e402e6e1b780f6565539ae0acb3e2976fb9 added a
  new timer class to chrome that is capable of waking the
  system from suspend. shill and powerd also need to use
  this timer but unfortunately the git mirror for the
  directory where the timer class lives has not been set up
  yet and it's probably too close to the branch point now to
  risk trying to uprev libchrome anyway.  Instead we can
  backport that particular CL into the chrome os tree until
  the next time we update libchrome.

This adds the components/ directory from Chrome OS's
libchrome package, as pulled in by the following commits:

  https://chromium-review.googlesource.com/226183
  https://chromium-review.googlesource.com/227460
  https://chromium-review.googlesource.com/234450

Bug: 22317122
Change-Id: I23630e2eac709aa86340435c44b822f58245d36a
5 files changed