We recently added code to disable accelerated compositing under Wayland (bug 120347).
However that code is located in WebKitWebViewGroup, which is not used by WebKitTestRunner.
One option would be to move it to webkitWebViewBaseUpdatePreferences().
But I think it would be better to just disable AC in all cases unless we actually support it, something like:
Created attachment 210590 [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
Comment on attachment 210590 [details]
Makes sense to me. It's a bit weird conceptually that we set a pagegroup-wide policy in each view, but it seems to be the most practical way of handling this issue, and we were already doing that anyway.
Committed r155125: <http://trac.webkit.org/changeset/155125>