GitLab

Optionally call GetCurrentPTS() for every call to GetMediaTime(),
instead of every 250ms. Also update the ALSA version of GetCurrentPts()
to be more accurate.

BUG= internal b/64273974

Change-Id: I8fbbae970baba8b6207838756f8ed3513ee629a2
Reviewed-on: https://chromium-review.googlesource.com/661717Reviewed-by: Sergey Volk <servolk@chromium.org>
Reviewed-by: Luke Halliwell <halliwell@chromium.org>
Commit-Queue: Kenneth MacKay <kmackay@chromium.org>
Cr-Commit-Position: refs/heads/master@{#501524}