Mac Metal style does not allow dragging of windows by dragging on the metal

Native Mac applications that uses the metal style allows the window to be dragged when dragging on the mental.

When brushed metal is on, the user should be able to drag the window by any part of the brushed metal, not just the title bar. The reason is that under brushed metal there is no clear visual distinction on the title bar. Expecting the users to drag using the title bar (which they can't see) is not good - and its not how brushed metal works on the Mac.

Reproducible with the following code:
#include <QtGui>
#include <QDebug>
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QWidget widget;
widget.setAttribute(Qt::WA_MacMetalStyle);
widget.show();
return app.exec();
}