Revert of Removing silence trimming from WebRTC quality test.

Revert of Removing silence trimming from WebRTC quality test. (patchset #5 id:80001 of https://codereview.chromium.org/890893004/)

Reason for revert:
This actually made the score worse by about 0.4 on all bots except one, and one bot is still not helped by this. I will try to solve this through other means, like forcing the volume to the right level on the bots where we get bad scores.

Original issue's description:
> Removing silence trimming from WebRTC quality test
>
> It turns out PESQ can deal with delays, so we don't need to
> silence-trim the files to get them to line up. This solves another
> problem where the silence-trimming becomes too aggressive on Windows
> with the new ref file.
>
> I also need to monitor if the new ref file, which is a lot lower
> in volume than the old one, unfairly punishes the score. The
> speaker volume is a bit random on the bots so the recording could
> end up being quite low. Tests on my workstation suggests that PESQ
> is actually pretty good about ignoring that too though. There will
> be a slight effect on the score (like 0.4 MOS), which I think is
> acceptable. Otherwise we need to find a way to control the speaker
> volume on the bots much more stringently.
>
> BUG=446859
>
> Committed: https://crrev.com/36d358e0cdff201a99501e9c986a8a26f8965a40
> Cr-Commit-Position: refs/heads/master@{#314797}

TBR=henrika@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=446859
Committed: https://crrev.com/218b32ccfa3202d84c8f17f6fb3420c4769cb88a
Cr-Commit-Position: refs/heads/master@{#315192}

[phoglund_chromium, 2015-02-07 12:22:22]

Created Revert of Removing silence trimming from WebRTC quality test.

[commit-bot: I haz the power, 2015-02-07 12:22:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/908703002/1

[commit-bot: I haz the power, 2015-02-07 12:23:14]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-07 12:23:54]

Patchset 1 (id:??) landed as
https://crrev.com/218b32ccfa3202d84c8f17f6fb3420c4769cb88a
Cr-Commit-Position: refs/heads/master@{#315192}