Kill audio process at audio thread hang.

* Introduce feature AudioServiceOutOfProcessKillAtHang with timeout parameter.
* If feature is enabled, kill process when audio thread is detected
  as hung, using timeout (or default timeout).
* Add info about feature and parameter in media-internals.

Enable with command line flags
--enable-features=AudioServiceAudioStreams,AudioServiceOutOfProcess,"AudioServiceOutOfProcessKillAtHang<MyStudyName" --force-fieldtrials=MyStudyName/Group1 --force-fieldtrial-params=MyStudyName.Group1:timeout_seconds/60

Bug: 963810
Change-Id: Ic05a552763452855982ae76dc92c4b04872b0220
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1615018
Reviewed-by: Olga Sharonova <olka@chromium.org>
Reviewed-by: Max Morin <maxmorin@chromium.org>
Commit-Queue: Henrik Grunell <grunell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661404}
8 files changed