It needs fullscreen API support.
This test is all written in terms of "mousemove" and "click" events. Even enabling fullscreen support isn't sufficient to cause the test to pass.
I've got some changes which enable the fullscreen API for WebKitTestRunner (that project doesn't use FeatureDefines.xcconfig, strangely) and that changes fullscreen.js to use `internals.withUserGesture()` rather than `eventSender`. But the test still times out because it's waiting for a "mousemove" and "click" event that will never come on iOS.
Created attachment 380660 [details]