QFileDialog::getSaveFileName does not put requested file name into native file dialog on Mac OS X - broken since Qt 4.8

If the third parameter passed to QFileDialog::getSaveFileName contains a file pathname, then the save dialog should point to that directory path (which it does) AND pass the filename to the dialog (which appears to be broken). You can see the problem in the Qt example application 'sdi'. Launch sdi, open a text file, then select File -> Save As... The resulting dialog has an empty file name. It should have the name of the file you've just tried to save.

I've downloaded the latest git repository version of Qt, built and tested against that as well as against beta 2. I've tested under OS X 10.7 and 10.8, and the problem is seen consistently. I've checked that a valid pathname is passed to QFileDialog::getSaveFileName.

QFileDialog::getSaveFileName works as expected when built with Qt 4.8, but not with Qt 5.0 beta 2.