Layer effects do not work on QQuickWindow::contentItem

import QtQuick 2.7
import QtQuick.Window 2.2

Window {
    id: window
    width: 360
    height: 360
    visible: true
    title: "contentItem"

    contentItem.layer.enabled: true
    contentItem.layer.effect: ShaderEffect { }

    Text {
        text: "Content"
        font.pixelSize: 72
        anchors.centerIn: parent
    }
}

import QtQuick 2.7
import QtQuick.Window 2.2
import QtGraphicalEffects 1.0

Window {
    id: window
    width: 360
    height: 360
    visible: true
    title: "otherItem"

    Item {
        id: otherItem
        anchors.fill: parent

        layer.enabled: !window.active
        layer.effect: FastBlur {
            source: otherItem
            radius: 32
        }

        Text {
            color: "green"
            text: "Other"
            font.pixelSize: 72
            anchors.centerIn: parent
        }
    }
}

Window::contentItem
├─ ApplicationWindow::contentItem
└─ ApplicationWindow::overlay