Unable to extend *QQuickApplicationWindow* and *QQuickMaterialTextContainer*

If a customized class extends QQuickApplicationWindow with QML_EXTENDED(QQuickApplicationWindow), the project will not be compilable, the failure cause is related to QtQml's internal C++ templates.

If a customized class extends QQuickMaterialTextContainer, the project will not be compilable too, this is because QQuickMaterialTextContainer moves the scope of void componentComplete() from protected to private.