/usr/lib/x86_64-linux-gnu/qt5/qml/QtWebKit/experimental/qmldir is in qml-module-qtwebkit 5.5.1+dfsg-2ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | module QtWebKit.experimental
plugin qmlwebkitexperimentalplugin
|