WPE doesn't support action commands because the platform specific code for handling events is not implemented.
Created attachment 346468 [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 r234543: <https://trac.webkit.org/changeset/234543>