Window Z-Order is okay at creation time, but broken when using "show" method

```
What steps will reproduce the problem?
1. Create a window and some interface behind it
2. Hide and show the window
3. http://dg-pic.tk/bacob

That wasn't the case in some previous version, can't tell exactly in which 
revision it was broken, but that thing is kinda annoying.
```

Original issue reported on code.google.com by `doctorge...@gmail.com` on 13 Aug 2014 at 3:02
