getUserMedia on chromeMediaSource "screen" doesn't work on Mac OSX

As where as getUserMedia fine working with a chromeMediaSource = "screen" on windows platform, unfortunatly the request return an empty content on MacOSX plateform

getUserMedia({
audio: false,
video: {
mandatory:

{ chromeMediaSource: "screen", maxWidth: 1280, maxHeight: 720 }

}
});