WebEngineView: Can't set the httpUserAgent after the view's initialization

import QtQuick 2.4
import QtWebEngine 1.1
WebEngineView {
    width: 600; height: 600
    url: "http://whatismyuseragent.com"
    Component.onCompleted: {
        profile.httpUserAgent = "foo"
        reload()
    }
}

import QtQuick 2.4
import QtWebEngine 1.1
import QtWebChannel 1.0
WebEngineView {
    width: 600; height: 600
    url: "http://whatismyuseragent.com"
    profile.httpUserAgent: "foo"
    webChannel.registeredObjects: []
}

import QtQuick 2.4
import QtWebEngine 1.1
WebEngineView {
    width: 600; height: 600
    url: "http://whatismyuseragent.com"
    profile.httpUserAgent: "foo"
    backgroundColor: "red"
}