Add comment in render_widget()

qutebrowser/browser/webengine/webview.py

@@ -64,6 +64,8 @@ class WebEngineView(QWebEngineView):
         Normally, this would always be the focusProxy().
         However, it sometimes isn't, so we use this as a WORKAROUND for
         https://bugreports.qt.io/browse/QTBUG-68727
+
+        This got introduced in Qt 5.11.0 and fixed in 5.12.0.
         """
         if 'lost-focusproxy' not in objreg.get('args').debug_flags:
             proxy = self.focusProxy()