This bug asks to examine ${java.home}/lib/content-types.properties to see whether it can be loaded as a resources file, from resources.jar. This follows JDK-8004963: "URLConnection, downgrade normative reference to ${java.home}/lib/content-types.properties".
The motive for this bug is the modular JDK where we need the flexibility to put anything that is module-private into a module-private location. In this case it would appear that the above files are not a supported interface and so should move to a location that should be read as resources.