Improve support for audio-device group IDs on Linux.

This is a reland of https://codereview.chromium.org/2258143002, originally authored by maxmorin@.
This version contains minor additions, lint fixes and restricts functionality to just non-ChromeOS
Linux.

This CL adds the following AudioManagerPulse overrides in order to better support group IDs:
  * GetDefaultInputDeviceID()
  * GetDefaultOutputDeviceID()
  * GetAssociatedOutputDeviceID()

The original CL was reverted due to regressions on ChromeOS with AudioManagerPulse. This CL keeps
behavior of AudioManagerPulse on ChromeOS unmodified.

Bug: 636300
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: Id48dc1477efd2fecd5ae111df22dfe2b744de6e0
Reviewed-on: https://chromium-review.googlesource.com/1072649
Commit-Queue: Guido Urdaneta <guidou@chromium.org>
Reviewed-by: Max Morin <maxmorin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#561855}
5 files changed