function _setupOS() {
		var html = document.documentElement;
		html.dataset.sapUiOs = Device.os.name + Device.os.versionStr;
		var osCSS = null;
		if (Device.os.name === Device.os.OS.IOS) {
			osCSS = "sap-ios";
		} else if (Device.os.name === Device.os.OS.ANDROID) {
			osCSS = "sap-android";
		}
		if (osCSS) {
			html.classList.add(osCSS);
		}
	}
Set the body's OS-related attribute and CSS class
@private