Revert of Requiring confidence in initial regression range before bisecting.

Revert of Requiring confidence in initial regression range before bisecting. (patchset #4 id:110001 of https://codereview.chromium.org/644323002/)

Reason for revert:
Bisect is broken because the ConfidenceScore expects list of list, but here only list is passed.
http://build.chromium.org/p/tryserver.chromium.perf/builders/linux_perf_bisect/builds/693/steps/Running%20Bisection/logs/stdio

Original issue's description:
> Requiring confidence in initial regression range before bisecting.
>
> BUG=422727
>
> Committed: https://crrev.com/4436048a948a2010062d3c6a171775d9389fd732
> Cr-Commit-Position: refs/heads/master@{#300196}

TBR=qyearsley@chromium.org,chrisphan@chromium.org,tonyg@chromium.org,robertocn@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=422727
Committed: https://crrev.com/5c1f219c38390434dc47e12a451c38703eaea6e1
Cr-Commit-Position: refs/heads/master@{#300280}

[prasadv, 2014-10-20 16:48:51]

Created Revert of Requiring confidence in initial regression range before
bisecting.

[commit-bot: I haz the power, 2014-10-20 16:49:56]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/661393003/1

[commit-bot: I haz the power, 2014-10-20 16:50:36]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-10-20 16:51:14]

Patchset 1 (id:??) landed as
https://crrev.com/5c1f219c38390434dc47e12a451c38703eaea6e1
Cr-Commit-Position: refs/heads/master@{#300280}