Revert of [Android] Migrate javascript settings to a content setting from a pref.

Revert of [Android] Migrate javascript settings to a content setting from a pref. (patchset #3 id:40001 of https://codereview.chromium.org/920583002/)

Reason for revert:
This breaks the ContentSettings#getJavaScriptEnabled, so that dependency needs to be cleared up.

Original issue's description:
> [Android] Migrate javascript settings to a content setting from a pref.
>
> This also adds a preferences migration function and tracking system to
> handle future changes.
>
> BUG=454063
>
> Committed: https://crrev.com/c404e85f318501565ebd0c8b3541fbc2e260b158
> Cr-Commit-Position: refs/heads/master@{#316023}

TBR=newt@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=454063
Committed: https://crrev.com/f38a80da741a08c5bf722226a06325b784a40909
Cr-Commit-Position: refs/heads/master@{#316045}

[Ted C, 2015-02-12 20:52:57]

Created Revert of [Android] Migrate javascript settings to a content setting
from a pref.

[commit-bot: I haz the power, 2015-02-12 20:53:39]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/923573003/1

[commit-bot: I haz the power, 2015-02-12 20:54:20]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-12 20:55:13]

Patchset 1 (id:??) landed as
https://crrev.com/f38a80da741a08c5bf722226a06325b784a40909
Cr-Commit-Position: refs/heads/master@{#316045}