Revert of Optimizes the operation of DeleteDatabase when no backing store exists.

Revert of Optimizes the operation of DeleteDatabase when no backing store exists. (patchset #5 id:120001 of https://codereview.chromium.org/1071553002/)

Reason for revert:
This appears to have made IndexedDBBrowserTest.DiskFullOnCommit flaky, starting at http://build.chromium.org/p/chromium.memory.fyi/builders/Windows%20Content%20Browser%20%28DrMemory%20full%29%20%286%29/builds/380

[ RUN      ] IndexedDBBrowserTest.DiskFullOnCommit

[1028:1768:0423/085845:4229748:INFO:mock_browsertest_indexed_db_class_factory.cc(258)] FailOperation: class=2, method=2, instanceNum=5, callNum=1
[1028:1768:0423/085845:4229873:INFO:indexed_db_browsertest.cc(77)] Navigating to URL and blocking.
[3872:2724:0423/085859:4243383:ERROR:renderer_main.cc(200)] Running without renderer sandbox

[1028:1096:0423/085958:4302491:ERROR:indexed_db_backing_store.cc(4197)] IndexedDB Write Error: TRANSACTION_COMMIT_METHOD
[1028:1768:0423/090005:4309621:INFO:indexed_db_browsertest.cc(79)] Navigation done.
c:\b\build\slave\drm-cr\build\src\content\browser\indexed_db\indexed_db_browsertest.cc(88): error: Failed
Failed: Starting...<span>FAILED: unexpectedErrorCallback<br></span>
[  FAILED  ] IndexedDBBrowserTest.DiskFullOnCommit, where TypeParam =  and GetParam() =  (130664 ms)

Original issue's description:
> Optimizes the operation of DeleteDatabase when no backing store 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.
>
> BUG=460236
>
> Committed: https://crrev.com/a4c618a142515773709688bfe3c5753e589afd43
> Cr-Commit-Position: refs/heads/master@{#326473}

TBR=cmumford@chromium.org,jsbell@chromium.org,payal.pandey@samsung.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=460236
Committed: https://crrev.com/66c83b1fd5e97358046b9fec051d2ce63530194a
Cr-Commit-Position: refs/heads/master@{#326686}

[Jeffrey Yasskin, 2015-04-23 23:03:11]

Created Revert of Optimizes the operation of DeleteDatabase when no backing
store exists.

[commit-bot: I haz the power, 2015-04-23 23:03:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1106703003/1

[commit-bot: I haz the power, 2015-04-23 23:05:08]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-23 23:06:00]

Patchset 1 (id:??) landed as
https://crrev.com/66c83b1fd5e97358046b9fec051d2ce63530194a
Cr-Commit-Position: refs/heads/master@{#326686}