xwayland: allow windows to scale themselves

wire/jay_compositor.txt

@@ -92,6 +92,10 @@ request create_ei_session (since = 5) {
     id: id(jay_ei_session_builder),
 }
 
+request get_xwayland (since = 11) {
+    id: id(jay_xwayland),
+}
+
 # events
 
 event client_id {

wire/jay_xwayland.txt

@@ -0,0 +1,18 @@
+# requests
+
+request get_scaling {
+}
+
+request set_scaling_mode {
+    mode: u32,
+}
+
+# events
+
+event scaling_mode {
+    mode: u32,
+}
+
+event implied_scale {
+    scale: i32,
+}