Since GTK 3.14 "gtk_misc_set_alignment" has been deprecated. "gtk_widget_set_halign" and "gtk_widget_set_valign" should be used instead, both available since GTK 3. I'll attach a patch.
Created attachment 371947 [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 371947 [details] Patch Clearing flags on attachment: 371947 Committed r246351: <https://trac.webkit.org/changeset/246351>
All reviewed patches have been landed. Closing bug.