QWebEngineView::print() can produce pixellated results on QPrintPreviewDialog

Steps to reproduce

1. Build and run the WebEngine Widgets PrintMe Example: https://doc.qt.io/qt-6/qtwebengine-webenginewidgets-printme-example.html
2. Activate the Print Preview by pressing Ctrl+P, then set the zoom level to 100%
3. Click the "Print" button on the top-right corner of QPrintPreviewDialog, and do an actual print (e.g. "Microsoft Print to PDF")
4. Repeat Step #2

Outcomes

• (Qt 6) We get a bad image at Step #2 but a good image at Step #4
• (Qt 5) We get a bad image at both Steps #2 and #4

Outcomes updated July 7, 2025

• Attached new outcomes as the old ones in the original issue do not show the severe nature of the blurriness.
• Attached: "printmetest.pdf" is generated using the Qt printme example (Bad case)
• Attached: "Superbill View.pdf" is generated using raw Chromium (not the Qt version) do show that pure Chromium does not have the issue.

Bad:

Good: