window-x11: Fix unredirection for windows that explicitly set bounding

Some applications, like Chromium, explicitly set their bounding region
to the client area when full-screen. Detect this case, and allow us to
fullscreen when this happens.

src/x11/window-x11.c

@@ -1847,6 +1847,12 @@ meta_window_x11_update_shape_region (MetaWindow *window)
        * this is simply the client area.
        */
       cairo_region_intersect_rectangle (region, &client_area);
+
+      /* Some applications might explicitly set their bounding region
+       * to the client area. Detect these cases, and throw out the
+       * bounding region in this case. */
+      if (cairo_region_contains_rectangle (region, &client_area) == CAIRO_REGION_OVERLAP_IN)
+        g_clear_pointer (&region, cairo_region_destroy);
     }
 
   meta_window_set_shape_region (window, region);