/usr/share/java/tomcat8-websocket-api.jar is in libtomcat8-java 8.5.30-1ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/java/tomcat8-websocket-api-8.5.30.jar
/usr/share/java/tomcat8-websocket-api-8.5.30.jar