Windows: Flash contents not shown when top level window has WA_TranslucentBackground and Qt::FramelessWindowHint

In order to have translucent top level windows on Windows, the window has to have both WA_TranslucentBackground and Qt::FramelessWindowHint set.

However, if such a top level window contains a QWebView showing a web page with Flash contents, the Flash contents are not shown. The audio of the Flash contents can be heard as expected, though.

The problem can be easily reproduced by loading a web page with Flash content in the example from the Transparent QWebView blog on Qt Labs: http://labs.qt.nokia.com/blogs/2009/06/30/transparent-qwebview-or-qwebpage/

The problem does not occur if only one of WA_TranslucentBackground or Qt::FramelessWindowHint is set.

The problem is not reproducible on Linux.