Add metrics collection for bitstream audio output support.

This will provide insight into the number of devices which we could
pass AC3, DTS, Dolby TrueHD, Dolby Digital Plus, or DTS-HD to.

BUG=928562
TEST=shows supported on my local HTPC.

Change-Id: I4ba4639736802b06e88995c23a7ecc6936dfae62
Reviewed-on: https://chromium-review.googlesource.com/c/1461676
Reviewed-by: Brian White <bcwhite@chromium.org>
Commit-Queue: Dale Curtis <dalecurtis@chromium.org>
Auto-Submit: Dale Curtis <dalecurtis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#631870}
2 files changed