Although the QBackingStore constructor takes a QWindow* as a parameter,
it does not inherit QObject and doesn't become a QObject child of the
QWindow. Use QScopedPointer to avoid memory leaks.
Pick-to: 6.2
Change-Id: Ib065163a9149d002f8220a0257bd78549062c595
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Paul Wicking <paul.wicking@qt.io>
c4856a9075