WebEngineView's zoomFactor property doesn't work

import QtQuick 2.5
import QtQuick.Controls 1.4
import QtWebEngine 1.2
import QtQuick.Window 2.2

ApplicationWindow {
  id: root
  objectName: "root"
  width: Screen.width
  height: Screen.height
  maximumHeight: height
  minimumHeight: height
  maximumWidth: width
  minimumWidth: width
  visible: true
  visibility: "FullScreen"

  WebEngineView {
    id: webview
    url: "http://www.google.fi"
    anchors.fill: parent
    zoomFactor:5;
    onZoomFactorChanged:{
        console.log("zoom")
        zoomFactor=1.0;
    }
  }
}