Revert of Revert of [1b] Implement FetchBlobDataConsumerHandle

Revert of Revert of [1b] Implement FetchBlobDataConsumerHandle (patchset #1 id:1 of https://codereview.chromium.org/1207273003/)

Reason for revert:
Relanding.

Original issue's description:
> Revert of [1b] Implement FetchBlobDataConsumerHandle (patchset #18 id:320001 of https://codereview.chromium.org/1176403006/)
> 
> Reason for revert:
> May have broken IndexedDBBrowserTestWithGCExposed.BlobDidAck.
> 
> Original issue's description:
> > Implement FetchBlobDataConsumerHandle
> > 
> > Unit tests will be added in https://codereview.chromium.org/1199043004/.
> > 
> > FetchInitiatorTypeNames.in is modified to use FetchInitiatorTypeNames::internal from modules/.
> > 
> > BUG=480746
> > 
> > Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=198220
> 
> TBR=haraken@chromium.org,mkwst@chromium.org,oilpan-reviews@chromium.org,yhirano@chromium.org,hiroshige@chromium.org
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=480746
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=198229

TBR=haraken@chromium.org,mkwst@chromium.org,oilpan-reviews@chromium.org,yhirano@chromium.org,hiroshige@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=480746
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=198237

[dcheng, 2015-07-02 18:20:26]

Created Revert of Revert of [1b] Implement FetchBlobDataConsumerHandle

[commit-bot: I haz the power, 2015-07-02 18:20:38]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1226563002/1

[commit-bot: I haz the power, 2015-07-02 18:21:06]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=198237

[haraken, 2015-07-02 22:05:53]

LGTM