Disable clutter's high dpi scaling

mutter needs some work to work with high dpi scaling so disable
the scaling until that is fixed.

https://bugzilla.gnome.org/show_bug.cgi?id=723931

src/core/main.c

@@ -455,6 +455,13 @@ meta_init (void)
        */
       meta_clutter_init ();
     }
+
+  /*
+   * XXX: We cannot handle high dpi scaling yet, so fix the scale to 1
+   * for now.
+   */
+  clutter_settings = clutter_settings_get_default ();
+  g_object_set (clutter_settings, "window-scaling-factor", 1, NULL);
 }
 
 /**