QApplication::setWindowIcon is no longer changing the dock icon on OSX

This is a regression from Qt4

QGuiApplication::setWindowIcon does not change the dock icon on mac.

Testcase:

#include <QApplication>
#include <QWidget>
#include <QImage>
#include <QIcon>
 
int main(int argc, char **argv) {
    QApplication app(argc, argv);
    QImage i(32,32, QImage::Format_RGB32);
    i.fill(Qt::blue);
    QApplication::setWindowIcon(QIcon(QPixmap::fromImage(i)));
    QWidget w;
    w.show();
    return app.exec();
}

According to the apple documentation https://developer.apple.com/library/mac/documentation/Carbon/Conceptual/customizing_docktile/docktasks_cocoa/docktasks_cocoa.html one need to call [NSApp setApplicationIconImage] to update the dock icon.
Qt4 did that by qt_mac_set_app_icon calling in QApplication::setWindowIcon http://code.woboq.org/kde/qt4/src/gui/kernel/qapplication.cpp.html#2125
The implementation of qt_mac_set_app_icon
http://code.woboq.org/kde/qt4/src/gui/kernel/qapplication_mac.mm.html#471

In qt5 however, git grep setApplicationIconImage returns no results, and even Q(Gui)ApplicationPrivate::notifyWindowIconChanged does not notify the platform plugin that the icon has changed.