Back when doclint was introduced, to avoid some duplicate messages, a pragmatic decision was made to disable warnings generated by the Standard Doclet when DocLint was enabled.

This had the unexpected side effect of disabling the effect of the `-serialwarn` when DocLint was enabled, which is the default case in the main JDK build.

Fixing JDK-8252717 will implicitly fix `-serialwarn` which exposes 413 warnings in the JDK build.
The warnings are all about missing @serial tags, of the following form

open/src/jdk.jdi/share/classes/com/sun/jdi/ClassNotLoadedException.java:74: warning: in class com.sun.jdi.ClassNotLoadedException, missing @serial tag for default serializable field: className.
    private String className;
                   ^

The warnings are distributed as follows:

 238 src/java.base
 111 src/java.desktop
  14 src/java.xml
  14 src/java.management
   8 src/jdk.jshell
   7 src/java.sql.rowset
   5 src/jdk.jdi
   3 src/java.sql
   3 src/java.scripting
   2 src/java.datatransfer
   1 src/jdk.xml.dom
   1 src/jdk.dynalink
   1 src/jdk.attach
   1 src/java.xml.crypto
   1 src/java.smartcardio
   1 src/java.security.jgss