Please describe the problem:
When trying to minimize all windows on the Win32 desktop via "Minimize All", e.g. available via Windows-button+M, Gtk transient windows stay open - unlike when individual main windows are minimized using the minimize button.

Steps to reproduce:
1. Start the test application that will be attached shortly (after building it.)
2. Select File->About...
3. Click the minimize button.
4. Restore the windows
5. Press Windows+M


Actual results:
After step 3, both windows belonging to the test appliaction - "mywindow" and "aboutwindow", are minimized. On step 5, only the mainwindow is. "aboutwindow", which is transient for "mywindow", will still be visible.

Expected results:
The minimize behaviour should be exactly the same in both cases.

Does this happen every time?
Yes

Other information:
This is probably related to other transient window issues fixed lately - see e.g. bug 504984.