Adding libpulse-dev to build on Linux

We are going to use PulseAudio IO as the default audio implementation for Chrome on Linux. We need the development header to build chromium.

This is needed for https://codereview.chromium.org/12310101/

TBR=dalecurtis@chromium.org
BUG=178101
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=186731

[no longer working on chromium, 2013-03-07 13:36:04]

Dale, I think we should land this before
https://codereview.chromium.org/12310101/, so that all the bots have the
headers.

SX

[no longer working on chromium, 2013-03-07 14:38:46]

Dale, I am going to leave the office a bit earlier today, probably I am not able
to wait for your lgt* on this CL. I suppose it is fine to land this now and send
out the PSA today to save one day. :)

[commit-bot: I haz the power, 2013-03-07 15:10:17]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/xians@chromium.org/12613005/1

[commit-bot: I haz the power, 2013-03-07 17:07:51]

Change committed as 186731

[DaleCurtis, 2013-03-07 19:06:09]

lgtm