The com.sun.webkit.dom Java wrappers, which are generated by the native WebKit build, are also checked into modules/web/src/main/java-wrappers/com/sun/webkit/dom so that the Java code can build without requiring a build of the native WebKit.
These files need to be refreshed following the r197500 WebKit update in JDK-8166999, since the updated webkit has changed the generated wrappers.
See JDK-8157384 for the last time this was done. The basic recipe is:
1. Build FX 9-dev with -PCOMPILE_WEBKIT=true
2. Copy the .java files from modules/javafx.web/build/gensrc/java/com/sun/webkit/dom/*.java to modules/javafx.web/src/main/java-wrappers/com/sun/webkit/dom/
3. Build FX 9-dev again, this time with -PCOMPILE_WEBKIT=false (as a sanity test to make sure it still builds).
4. Create a webrev with the changes for the java-wrappers