xwayland: handle rare case of focus_in event occurring before map

This fixes a timing-dependent issue where the CLion main window was
sometimes not correctly focused at startup.

include/xwayland.h

@@ -39,6 +39,7 @@ struct xwayland_unmanaged {
 struct xwayland_view {
 	struct view base;
 	struct wlr_xwayland_surface *xwayland_surface;
+	bool focused_before_map;
 
 	/* Events unique to XWayland views */
 	struct wl_listener associate;