Right now file chooser dialogs are never run as modal by default. It would be desirable to try to obtain the GtkWindow where the GtkWebView is embedded, set it as parent of the dialogs, and enable running them as modal.
Created attachment 304203 [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
Comment on attachment 304203 [details] Patch Although possibly applications might not want this behavior, this definitely ought to be the default behavior to avoid unexpected bugs in applications.
Comment on attachment 304203 [details] Patch Clearing flags on attachment: 304203 Committed r213772: <http://trac.webkit.org/changeset/213772>
All reviewed patches have been landed. Closing bug.