[REG 5.10 -> 5.11] Keyboard focus issues

After https://codereview.qt-project.org/#/c/221408/ (cc juri.valdmann) I'm seeing some issues with keyboard focus not going to the page when it should.

I'm seeing it in various scenarios, here's one way to reproduce it:

With this simple code:

#include <QApplication>
#include <QWebEngineView>
#include <QUrl>

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QWebEngineView view;
    view.load(QUrl(argv[1]));
    view.show();
    return app.exec();
}

QT += core widgets webenginewidgets

TARGET = testbrowser
TEMPLATE = app

SOURCES += main.cpp

When doing ./testbrowser https://ddg.gg, I see the keyboard focus on the search field (blinking cursor), but the keyboard input goes nowhere.

Some observations:

• With simplebrowser, the keyboard focus doesn't show up on that input at all.
• When setting FocusOnNavigationEnabled it doesn't happen (but that has other drawbacks).
• Before that change, it doesn't happen.
• When loading https://duckduckgo.com/ directly, it doesn't seem to happen.

I'm seeing it in other situations as well, but this is probably the easiest one to reproduce.