Revert of Fix content verifier problem with content scripts

Revert of Fix content verifier problem with content scripts (patchset #3 id:40001 of https://codereview.chromium.org/1226163010/)

Reason for revert:
The ContentVerifierTest.ContentScripts test introduced in this change has been failing
consistently on Vista. See below

http://build.chromium.org/p/chromium.win/builders/Vista%20Tests%20%281%29/builds/57878
http://build.chromium.org/p/chromium.win/builders/Vista%20Tests%20%281%29/builds/57877

Original issue's description:
> Fix content verifier problem with content scripts
>
> The problem is that we were creating the ContentVerifier too late
> in ExtensionSystemImpl::Shared::Init, after the script loader had
> already tried grabbing a reference to it for use on another
> thead. Therefore at run time, for all content scripts we were was
> seeing a null pointer for the content verifier and skipping
> verification of those scripts.
>
> BUG=509130
>
> Committed: https://crrev.com/fe6dc62c549db502a0323ebbebab7ffd4f5cebd7
> Cr-Commit-Position: refs/heads/master@{#339283}

TBR=rockot@chromium.org,asargent@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=509130
Committed: https://crrev.com/b9e8b50e4c45d8aefacac58e28c50d83bb257b7b
Cr-Commit-Position: refs/heads/master@{#339361}

[kelvinp, 2015-07-18 00:07:23]

Created Revert of Fix content verifier problem with content scripts

[commit-bot: I haz the power, 2015-07-18 00:08:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1243533005/1

[commit-bot: I haz the power, 2015-07-18 00:09:45]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-07-18 00:11:00]

Patchset 1 (id:??) landed as
https://crrev.com/b9e8b50e4c45d8aefacac58e28c50d83bb257b7b
Cr-Commit-Position: refs/heads/master@{#339361}