"The error event from an event listener should fire on that listener's global." per WPT but sometimes doesn't

[pshaughn]

The four tests with filenames WPT html/webappapis/scripting/processing-model-2/window-onerror-with-cross-frame-event-listeners-?.html test various slightly different scenarios that mix together objects from different (same-origin) globals to see which event handlers fire on which events. Tests -1.html and -4.html fail while 2 and 3 succeed; I'm not confident enough to speculate which aspect of the tests makes the difference.