sizerequest: ensure resize in get_request_mode
gtk_widget_get_request_mode is used to decide how size should be requested in gtk_widget_size_allocate_with_baseline, gtk_scrolled_window_allocate, gtk_window_guess_default_size and _gtk_widget_get_preferred_size_and_baseline.
As widgets can change size request mode we should ensure that cache is cleared (if resize has been queued) to make sure that correct size request mode is used.