JSUIScriptController::sendEventStream() crashes on the GLib platform as it is not implemented. As such, to maintain test coverage for WPTs exercising the wheel Actions interface, we should alter our implementation for the GLib port. This will involve adding an IDL field to the test runner to indicate if we're on GLib, and then using said field to fall back to maybe an `EventSender`-based implementation of the wheel Actions interface.
<rdar://problem/121074704>