Expose the DataTransferItem interface

Expose the DataTransferItem interface

https://html.spec.whatwg.org/#the-datatransferitem-interface

Both Firefox Nightly and IE11 expose the DataTransfer interface, but
neither DataTransferItem nor DataTransferItemList. We already expose
DataTransferItemList. Per spec all three interfaces should be exposed.

This will allow feature detection of the methods on DataTransferItem, in
particular DataTransferItem.prototype.webkitGetAsEntry, the lack of
which has forced at least one library to resort to UA string sniffing:
https://github.com/FineUploader/fine-uploader/issues/1346

BUG=448696
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=188382

[philipj_slow, 2015-01-14 13:15:57]

philipj@opera.com changed reviewers:
+ jochen@chromium.org

[philipj_slow, 2015-01-14 13:15:58]

Jochen, can you PTAL as this trivial but Web-exposed change?

[jochen (gone - plz use gerrit), 2015-01-14 13:28:45]

lgtm

[philipj_slow, 2015-01-14 13:32:00]

The CQ bit was checked by philipj@opera.com

[commit-bot: I haz the power, 2015-01-14 13:32:33]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/850863002/1

[commit-bot: I haz the power, 2015-01-14 13:36:27]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=188382