hidpi: Make sure gdk and clutter scaling stays disabled when the scale factor changes

Not doing that could led to messy situations when the user changes the scale factor
at runtime.

https://bugzilla.gnome.org/show_bug.cgi?id=726238

src/shell-global.c

@@ -760,6 +760,10 @@ update_scale_factor (GtkSettings *settings,
   g_value_init (&value, G_TYPE_INT);
   if (gdk_screen_get_setting (global->gdk_screen, "gdk-window-scaling-factor", &value))
     g_object_set (context, "scale-factor", g_value_get_int (&value), NULL);
+
+  /* Make sure clutter and gdk scaling stays disabled */
+  g_object_set (clutter_settings_get_default (), "window-scaling-factor", 1, NULL);
+  gdk_x11_display_set_window_scale (gdk_display_get_default (), 1);
 }
 
 /* This is an IBus workaround. The flow of events with IBus is that every time