Revert of Reland: Optimizes IndexedDB's DeleteDatabase when no db exists

Revert of Reland: Optimizes IndexedDB's DeleteDatabase when no db exists (patchset #1 id:1 of https://codereview.chromium.org/1216573008/)

Reason for revert:
Some bots still flaky. See crbug.com/506467

Original issue's description:
> Reland: Optimizes IndexedDB's DeleteDatabase when no db exists
>
> When deleting the non existing database in a origin with no existing
> backing store, then in DeleteDatabse(), early exiting before
> OpenBackingStore, so that it wont results in multiple transaction as
> earlier.
>
> Original patch by: payal.pandey
>
> This was reverted (see crrev.com/1071553002) when it appeared to make
> a test flaky, but the test continues to flake (now tracked as
> crbug.com/505609) so let's try relanding.
>
> BUG=460236
>
> Committed: https://crrev.com/4cbc8f1b383fb8145056295176912d53030a98b0
> Cr-Commit-Position: refs/heads/master@{#336796}

TBR=cmumford@chromium.org,jsbell@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=460236
Committed: https://crrev.com/4e132285cadc8875bd8bf5d0078f325562fdd620
Cr-Commit-Position: refs/heads/master@{#337228}

[vkuzkokov, 2015-07-02 16:18:10]

Created Revert of Reland: Optimizes IndexedDB's DeleteDatabase when no db exists

[commit-bot: I haz the power, 2015-07-02 16:18:23]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1225513002/1

[commit-bot: I haz the power, 2015-07-02 16:19:17]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-07-02 16:20:15]

Patchset 1 (id:??) landed as
https://crrev.com/4e132285cadc8875bd8bf5d0078f325562fdd620
Cr-Commit-Position: refs/heads/master@{#337228}

[vkuzkokov, 2015-07-02 16:51:59]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/1224533004/ by vkuzkokov@chromium.org.

The reason for reverting is: Test is still flaky..