Update a ton of audio code to use size_t more correctly and in general reduce

Update a ton of audio code to use size_t more correctly and in general reduce
use of int16_t/uint16_t.

This is the upshot of a recommendation by henrik.lundin and kwiberg on an original small change ( https://webrtc-codereview.appspot.com/42569004/#ps1 ) to stop using int16_t just because values could fit in it, and is similar in nature to a previous "mass change to use size_t more" ( https://webrtc-codereview.appspot.com/23129004/ ) which also needed to be split up for review but to land all at once, since, like adding "const", such changes tend to cause a lot of transitive effects.

This was be reviewed and approved in pieces:
https://codereview.webrtc.org/1224093003
https://codereview.webrtc.org/1224123002
https://codereview.webrtc.org/1224163002
https://codereview.webrtc.org/1225133003
https://codereview.webrtc.org/1225173002
https://codereview.webrtc.org/1227163003
https://codereview.webrtc.org/1227203003
https://codereview.webrtc.org/1227213002
https://codereview.webrtc.org/1227893002
https://codereview.webrtc.org/1228793004
https://codereview.webrtc.org/1228803003
https://codereview.webrtc.org/1228823002
https://codereview.webrtc.org/1228823003
https://codereview.webrtc.org/1228843002
https://codereview.webrtc.org/1230693002
https://codereview.webrtc.org/1231713002

The change is being landed as TBR to all the folks who reviewed the above.

BUG=chromium:81439
TEST=none
R=andrew@webrtc.org, pbos@webrtc.org
TBR=aluebs, andrew, asapersson, henrika, hlundin, jan.skoglund, kwiberg, minyue, pbos, pthatcher

Committed: https://chromium.googlesource.com/external/webrtc/+/dce40cf804019a9898b6ab8d8262466b697c56e0

[Peter Kasting, 2015-08-20 00:23:40]

The CQ bit was checked by pkasting@chromium.org

[commit-bot: I haz the power, 2015-08-20 00:23:57]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1230503003/100001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1230503003/100001

[commit-bot: I haz the power, 2015-08-20 00:23:58]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-08-20 00:24:00]

No L-G-T-M from a valid reviewer yet. Only full committers are accepted.
Even if an L-G-T-M may have been provided, it was from a non-committer,
_not_ a full super star committer.
See http://www.chromium.org/getting-involved/become-a-committer
Note that this has nothing to do with OWNERS files.

[Peter Kasting, 2015-08-20 00:45:56]

pkasting@chromium.org changed reviewers:
+ aluebs@webrtc.org, andrew@webrtc.org, asapersson@webrtc.org,
henrik.lundin@webrtc.org, henrika@webrtc.org, jan.skoglund@webrtc.org,
kwiberg@webrtc.org, minyue@webrtc.org, pbos@webrtc.org, pthatcher@webrtc.org

[Peter Kasting, 2015-08-20 00:46:18]

The CQ bit was checked by pkasting@chromium.org

[commit-bot: I haz the power, 2015-08-20 00:46:35]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1230503003/100001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1230503003/100001

[commit-bot: I haz the power, 2015-08-20 00:50:55]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-08-20 00:50:57]

Try jobs failed on following builders:
  presubmit on tryserver.webrtc (JOB_FAILED,
http://build.chromium.org/p/tryserver.webrtc/builders/presubmit/builds/424)

[niklas.enbom, 2015-08-20 16:52:35]

lgtm!

On 2015/08/20 00:50:57, commit-bot: I haz the power wrote:
> Try jobs failed on following builders:
>   presubmit on tryserver.webrtc (JOB_FAILED,
> http://build.chromium.org/p/tryserver.webrtc/builders/presubmit/builds/424)

[pbos-webrtc, 2015-08-24 10:28:21]

On 2015/08/20 16:52:35, niklas.enbom wrote:
> lgtm!
> 
> On 2015/08/20 00:50:57, commit-bot: I haz the power wrote:
> > Try jobs failed on following builders:
> >   presubmit on tryserver.webrtc (JOB_FAILED,
> > http://build.chromium.org/p/tryserver.webrtc/builders/presubmit/builds/424)

rs-lgtm

[Andrew MacDonald, 2015-08-24 17:44:31]

rs-lgtm

[Peter Kasting, 2015-08-24 21:53:02]

Committed patchset #13 (id:110001) manually as
dce40cf804019a9898b6ab8d8262466b697c56e0 (presubmit successful).