The lack of WS_CLIPCHILDREN will cause drawing artifacts, so ensure
we have WS_CLIPCHILDREN in our native window manual tests, and warn
if users inadvertently end up reparenting windows into a HWND that
doesn't have WS_CLIPCHILDREN set.
Change-Id: Ic4dac83882167562599d63f46232071c8c21b617
Reviewed-by: Zhao Yuhang <2546789017@qq.com>
Reviewed-by: Wladimir Leuschner <wladimir.leuschner@qt.io>
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>
Reviewed-by: Pavel Dubsky <pavel.dubsky@qt.io>
33d1ac4095