tests/stacking: Add test checking the initial size

https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1171

src/tests/meson.build

@@ -145,6 +145,7 @@ stacking_tests = [
   'unmaximize-new-size',
   'fullscreen-maximize',
   'restore-position',
+  'default-size',
 ]
 
 foreach stacking_test: stacking_tests

src/tests/stacking/default-size.metatest

@@ -0,0 +1,36 @@
+new_client x x11
+create x/1 csd
+
+resize x/1 300 400
+show x/1
+wait
+
+assert_size x/1 300 400
+
+resize x/1 200 300
+wait_reconfigure
+assert_size x/1 200 300
+
+hide x/1
+show x/1
+wait
+assert_size x/1 200 300
+
+
+new_client w wayland
+create w/1 csd
+
+resize w/1 300 400
+show w/1
+wait
+
+assert_size w/1 300 400
+
+resize w/1 200 300
+wait_reconfigure
+assert_size w/1 200 300
+
+hide w/1
+show w/1
+wait_reconfigure
+assert_size w/1 200 300