Media query for pixel density not working in QtWebView

[hien]

I am trying this, but it doesn't seem to be working in the web view.
@media
only screen and (-webkit-min-device-pixel-ratio: 2),
only screen and ( min--moz-device-pixel-ratio: 2),
only screen and ( -o-min-device-pixel-ratio: 2/1),
only screen and ( min-device-pixel-ratio: 2),
only screen and ( min-resolution: 192dpi),
only screen and ( min-resolution: 2dppx) {
#logo {
background: url(../img/logo@2x.png);
}
}

Opening the html file in safari works fine. I am using Qt5.1. Is this a bug? Thanks