Revert of [Storage] Consoliation of BlobItems with small size (patchset #8 id:140001 of https://codereview.chromium.org/821913004/)

Reason for revert:
This caused regression on some layout tests.
e.g.
http://build.chromium.org/p/chromium.webkit/builders/WebKit%20Mac10.6%20%28deps%29/builds/35407
fast/files/read-blob-async.html
fast/files/workers/worker-read-blob-async.html
fast/files/workers/worker-read-blob-sync.html
fast/files/workers/worker-read-file-constructor-async.html
http/tests/local/blob/send-data-blob.html
http/tests/navigation/beacon-same-origin.html
http/tests/websocket/bufferedAmount-after-send.html

Original issue's description:
> [Storage] Consolidation of BlobItems with small size
> https://bit.ly/AutoBlobToDisk
>
> R=michaeln, piman
> BUG=375297
>
> Committed: https://crrev.com/4e45f41babddb10985c8c0afb9b0b6b9e8356094
> Cr-Commit-Position: refs/heads/master@{#312770}

TBR=michaeln@chromium.org,piman@chromium.org,dmurph@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=375297

Review URL: https://codereview.chromium.org/869763003

Cr-Commit-Position: refs/heads/master@{#312782}
3 files changed