To get the amount of bytes already downloaded.
Created attachment 145758 [details] Patch
Thanks for the patch. If this patch contains new public API please make sure it follows the guidelines for new WebKit2 GTK+ API. See http://trac.webkit.org/wiki/WebKitGTK/AddingNewWebKit2API
Committed r119493: <http://trac.webkit.org/changeset/119493>