The problem is that we are creating the new soup request for the redirect before calling ResourceHandleClient::willSendRequest() so that any change made to the request by the client is ignored.
Created attachment 220109 [details]
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 r161176: <http://trac.webkit.org/changeset/161176>