We deliver the sources for the javafx.* modules to the JDK build in the modules_src directory. See JDK-8169396.

This was also intended to allow a combined JDK javadoc bundle to be built including the docs for the javafx.* modules. However, we currently only copy the .java files (and module-info.java.extra) into modules_src. We do not copy the package.html file nor any needed resources in the various doc-files directories. This will cause the javadoc-generated API docs to have missing content.