Remove apparently spurious DCHECK

Remove apparently spurious DCHECK

This DCHECK will be triggered when http://trac.webkit.org/changeset/145097 is
re-landed.

[abarth-chromium, 2013-03-07 20:31:37]

Sorry for the broad list of reviewers, but I wasn't sure who the best person to
review this CL might be.

Thanks!

[jamesr, 2013-03-07 20:53:36]

LGTM for OWNERS, but you probably want a subject matter expert to review for
concept.

[michaeln, 2013-03-07 21:55:41]

lgtm

The check is actually not sprurious, it indicates something is amiss with the
FormData inputs. We're being asked to upload something that no longer exists.
Unfortunately that actually happens because we use strings (urls) to identify
blobs and pass strings around (throught webcore and chromium alike) w/o much
concern for lifetimes. For example the webcore code in that patch creates a Blob
and then deletes it immediately after having scribbled down the URL value. The
DCHECK helps to identify those kind of mistakes.

I've got work in progress to resolve this. Can you take a look at
https://bugs.webkit.org/show_bug.cgi?id=108851 to help move that along.

[abarth-chromium, 2013-03-07 23:03:46]

I didn't land this patch.