Revert of Delete historical data usage from store when user clears data usage. (patch...

Revert of Delete historical data usage from store when user clears data usage. (patchset #7 id:120001 of https://codereview.chromium.org/1346623004/ )

Reason for revert:
I am going to speculatively revert this CL, it seems to have broken Linux Test Dbg bot, although I'm not completely sure, how.
More info in http://crbug.com/534248#c6.
BUG=534248

Original issue's description:
> Delete historical data usage from store when user clears data usage.
>
> Delete data usage in LevelDB in addition to clearing stats store in
> browser preferences.
>
> BUG=482442,461022
>
> Committed: https://crrev.com/7305eb15590a4a3b363eeed2f1ed1b8638ee37fe
> Cr-Commit-Position: refs/heads/master@{#349805}

TBR=bengr@chromium.org,kundaji@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=482442,461022

Review URL: https://codereview.chromium.org/1355123002

Cr-Commit-Position: refs/heads/master@{#349926}