alsa_output: Drain and pause pcm when stopping.

alsa_output: Drain and pause pcm when stopping.

Call snd_pcm_drain when the output's Stop() function is called.  This
will keep some alsa interfaces from repeating the last samples played
until Close() is called.  This will also guarantee that all samples are
played back if Close() is called immediately following Stop().

BUG=chromium-os:31211
TEST=Manual, play and pause youtube, both FLASH and HTML5 videos using
the following alsa plugins as a sink for alsa_output:  plug, hw, dmix,
pulse, cras, jack.  Observe that pauses are clean without repeated
samples.


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=138939

[dgreid, 2012-05-23 17:41:44]

This fixes audio samples looping after pausing a stream on ChromeOS(when using
alsa... see crosbug.com/129243) and on Linux when using certain alsa plugins.

I tested it most on Goobuntu.  Seems pretty strait-forward, let me know if I'm
missing a reason why this wasn't being done.

Thanks,

-dg

[scherkus (not reviewing), 2012-05-24 17:57:27]

LGTM w/ nit on whitespacing

nice fix!

http://codereview.chromium.org/10413075/diff/2001/media/audio/linux/alsa_outp...
File media/audio/linux/alsa_output.cc (right):

http://codereview.chromium.org/10413075/diff/2001/media/audio/linux/alsa_outp...
media/audio/linux/alsa_output.cc:337: // Finish playing samples and pause the
pcm.
nit: we're pretty generous with vertical whitespace, so we typically have a
blank line before each // comment unless it's the first line of a new scope
(rest of this file follows that style)

[commit-bot: I haz the power, 2012-05-24 21:13:16]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/dgreid@chromium.org/10413075/7001

[commit-bot: I haz the power, 2012-05-24 21:40:21]

Try job failure for 10413075-7001 on win for step "update".
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win&number...

Step "update" is always a major failure.
Look at the try server FAQ for more details.

[commit-bot: I haz the power, 2012-05-24 22:46:38]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/dgreid@chromium.org/10413075/7001

[commit-bot: I haz the power, 2012-05-25 00:16:48]

Change committed as 138939