disabled items in item views (regression)

Easy to reproduce. It's more noticeable on the Mac because the gray
background is more pronounced. But the same happens in Windows, simply
the color contrasts less.
Obvious example on the Mac:

1) Run the Qt example "Standarg dialogs"
2) Uncheck "Use native dialog"
3) click on QFileDialog::getOpenFileNames()
4) Select "File of type *.txt", to gray out non txt files (something
standard under OS X, not Windows).
5) Switch to "Detail View" (top right button in the dialog)

Result: the background of all non .txt stuff is gray and this is not
normal.
If you switch back to "List view", then the display is correct. Items
appear correctly disabled.

This is not something limited to QFileDialog, this affects all Qt application using items views (at least QTreeView and I think QTableView too)