QtWebEngine crashes

QtWebEngine crashes (as tested with WebEngine Quick Nano Browser).

Built QtWebEngine for 5.9.5 and 5.10.1 with proprietary codecs and attempted to navigate to Netflix and watch videos from within the WebEngine Quick Nano Browser.

I tried Widevine binaries 1.4.8.1008 for both 5.9.5 and 5.10.1 builds, and also tried 1.4.9.1076 for the 5.10.1 build.

For the 5.10.1 build tests, I included the patch for the following bug:

https://bugreports.qt.io/browse/QTBUG-66560

The patch involved replacing:
NOTREACHED();

in functions:
HWND ScreenWin::GetHWNDFromNativeView(gfx::NativeView window) const
gfx::NativeWindow ScreenWin::GetNativeWindowFromHWND(HWND hwnd) const

from file:

src\3rdparty\chromium\ui\display\win\screen_win.cc

with:
#ifndef TOOLKIT_QT
NOTREACHED();
#endif
 

When the debugger is attached the crashes seem to be recoverable (the continue debugging button can be pressed to proceed) even though they are logged with a LogSeverity of LOG_FATAL within Chromium's message handling.

Most of the errors seem to stem from the ppapi host.