Reland of Add experiment on weak ping delay during call set up time

Reland of Add experiment on weak ping delay during call set up time (patchset #1 id:1 of https://codereview.webrtc.org/1423443002/ )

Reason for revert:
This should be safe to land now.

Original issue's description:
> Revert of Add experiment on weak ping delay during call set up time (patchset #4 id:60001 of https://codereview.webrtc.org/1411883002/ )
>
> Reason for revert:
> guoweis - Here's the target that's failing:
> https://code.google.com/p/chromium/codesearch#chromium/src/third_party/libjingle/libjingle_nacl.gyp&l=17
>
> This has unfortunately been causing problems repeatedly for us since libjingle_nacl is maintained separately from libjingle (I don't know the history).
>
> The way this works for Chrome in general is that the FindFullName method is implemented in init_webrtc.cc in the overrides folder in Chrome and that hooks WebRTC up with Chrome's implementation.  I'm not sure if that's the right thing to do for nacl, how webrtc is initialized there etc.  I'll ping the nacl team for some help too offline and include you.  Reverting this change for now.
>
> Original issue's description:
> > Add experiment on weak ping delay during call set up time
> >
> > BUG=
> > R=pthatcher@webrtc.org
> >
> > Committed: https://crrev.com/3bf69b15f4c0c0ca4ab17c237084684a37bb8279
> > Cr-Commit-Position: refs/heads/master@{#10343}
>
> TBR=pthatcher@webrtc.org,juberti@webrtc.org,guoweis@webrtc.org
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=
>
> Committed: https://crrev.com/a01d44022355796d4fd86d00aae6d3263573b6f1
> Cr-Commit-Position: refs/heads/master@{#10350}

TBR=pthatcher@webrtc.org,juberti@webrtc.org,tommi@webrtc.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=

Committed: https://crrev.com/e26ce1b7a4644942b239ed788a737200762db3b3
Cr-Commit-Position: refs/heads/master@{#10379}

[guoweis_webrtc, 2015-10-23 00:49:18]

Created Reland of Add experiment on weak ping delay during call set up time

[commit-bot: I haz the power, 2015-10-23 00:49:22]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1406153005/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1406153005/1

[commit-bot: I haz the power, 2015-10-23 00:49:32]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-23 00:49:45]

Patchset 1 (id:??) landed as
https://crrev.com/e26ce1b7a4644942b239ed788a737200762db3b3
Cr-Commit-Position: refs/heads/master@{#10379}

[guoweis_webrtc, 2015-10-23 01:00:28]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.webrtc.org/1413843003/ by guoweis@webrtc.org.

The reason for reverting is: Still cause break on mac. reverting it again..