qt5.15.2 QWebEngineView is slow, QWebEnginePage's print function is very slow.

[haibianren]

Environment:
QT 5.15.2 MSVC2019 32bit
OS: window 10

Reproduce steps:

1. Open the printme exmaple，replace local html file with remote url (https://github.com/marketplace)

main.cpp

int main(int argc, char *argv[])
{
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
    QApplication app(argc, argv);

    QWebEngineView view;

////////////////////////////////// modification: 
//    view.setUrl(QUrl(QStringLiteral("qrc:/index.html"))); 
    view.setUrl(QUrl("https://github.com/marketplace"));
////////////////////////////////

    view.resize(1024, 750);
    view.show();

    PrintHandler handler;
    handler.setPage(view.page());

    auto printPreviewShortCut = new QShortcut(QKeySequence(Qt::CTRL + Qt::Key_P), &view);
    auto printShortCut = new QShortcut(QKeySequence(Qt::CTRL + Qt::SHIFT + Qt::Key_P), &view);

    QObject::connect(printPreviewShortCut, &QShortcut::activated, &handler, &PrintHandler::printPreview);
    QObject::connect(printShortCut, &QShortcut::activated, &handler, &PrintHandler::print);

    return app.exec();
}

2. build and run printme，it's slower to open the remote url. Press CTRL + P to preview the page to print，it takes 9-20 seconds, very slow. We tried QT5.9 to build and run printme example, it's very fast to open url, preview page to print.

[haibianren]

well, QT5.15.0 is fast, finally we choose QT5.15.0