QuickView::grabWindow() fails for semi-transparent native-rendering text on Windows

http://lancelot.intra.qt.io/SlowCycle6/tst_Scenegraph/auto-reports/Report_Mar31-021147.html shows that text_emoji.qml is broken in text lines 5 and 7. Those are NativeRendering with semi-transparent color.  But importantly, note that those lines were broken BEFORE also (i.e. the baseline images), just differently broken.

FWIW, the effective patch that caused the latest behavior change seems to be the following, a dependency update: 00b59c391e88d37dd09f187000416a3501a1e009

Now the interesting part is that running qmlscenegrabber -viewonly on the test machine displays text_emoji.qml just fine, including lines 5 and 7. But when grabbing the rendering, one gets the broken image. 

This happens for both OpenGL and D3D11 RHI backends.