Revert of Increase ThreadWatcher unresponsive threashold to 72 secs in dev

Revert of Increase ThreadWatcher unresponsive threashold to 72 secs in dev (patchset #1 id:20001 of https://codereview.chromium.org/588373002/)

Reason for revert:
chromecrash calculates the correct magic signature for jank/hangs on UI/IO/FILE threads. Reverting this change to get crash dumps if UI/IO/FILE threads don't respond for 9 pings (in 18 secs).

Original issue's description:
> Increase ThreadWatcher unresponsive threashold to 72 secs in Dev
>
> Increase the #of pings from 9 to 36 for Dev (72 secs of
> unresponsiveness).
>
> Increased it to reduce the number of crash dump reports
> we receive. Will revert back, when we can auto triage
> jank on UI/IO threads.
>
> BUG=352489
> R=sky@chromium.org
>
> Committed: https://crrev.com/64792b2912f3be895944800859042103f1ffd6b6
> Cr-Commit-Position: refs/heads/master@{#296268}

TBR=sky@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=352489
Committed: https://crrev.com/7e61f5a502b19017a174c08d04bd2f7024ee54c1
Cr-Commit-Position: refs/heads/master@{#307404}

[ramant (doing other things), 2014-12-09 02:34:16]

Created Revert of Increase ThreadWatcher unresponsive threashold to 72 secs in
dev

[commit-bot: I haz the power, 2014-12-09 02:35:45]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/783423002/1

[commit-bot: I haz the power, 2014-12-09 02:36:25]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-12-09 02:37:15]

Patchset 1 (id:??) landed as
https://crrev.com/7e61f5a502b19017a174c08d04bd2f7024ee54c1
Cr-Commit-Position: refs/heads/master@{#307404}