QML WebEngineView can not deal with key event

/* key event cannot work with WebEngineView*/
import QtQuick 2.1
import QtQuick.Controls 1.1
import QtWebEngine 1.0

ApplicationWindow {
    width: 1280
    height: 720
    visible: true
    WebEngineView {
        id: webview
        url: "http://www.qt-project.org"
        anchors.fill: parent

        focus: true;
        Keys.onPressed: {
            if(event.key == Qt.Key_Escape || event.key == Qt.Key_Back)
            {
                console.log("xxxxxxxxxxxxxxxxx");
                Qt.quit();
            }
            else
            {
                console.log("yyyyyyyyyyyyyyyyyyy");
            }
        }
    }

    Rectangle {
        anchors.fill: parent;

        focus: true;
        color: Qt.rgba(0, 0, 0, 0.2);

        Keys.onPressed: {
            if(event.key == Qt.Key_Escape || event.key == Qt.Key_Back)
            {
                console.log("xxxxxxxxxxxxxxxxx");
                Qt.quit();
            }
            else
            {
                console.log("yyyyyyyyyyyyyyyyyyy");
            }
        }
    }
}

/* key event work will  without WebEngineView*/
import QtQuick 2.1
import QtQuick.Controls 1.1
import QtWebEngine 1.0

ApplicationWindow {
    width: 1280
    height: 720
    visible: true
    Rectangle {
        anchors.fill: parent;

        focus: true;
        color: Qt.rgba(0, 0, 0, 0.2);

        Keys.onPressed: {
            if(event.key == Qt.Key_Escape || event.key == Qt.Key_Back)
            {
                console.log("xxxxxxxxxxxxxxxxx");
                Qt.quit();
            }
            else
            {
                console.log("yyyyyyyyyyyyyyyyyyy");
            }
        }
    }
}