javac in JDK 9 is now treating unchecked casts and conversions as errors. These need to be suppressed or we can't build.

client/jdk/src/share/classes/javax/swing/JLayer.java:653: warning: [unchecked] unchecked cast
        view = (V) f.get("view", null);
                        ^
  required: V
  found: Object
  where V is a type-variable:
    V extends Component declared in class JLayer
error: warnings found and -Werror specified
client/jdk/src/share/classes/javax/swing/text/AbstractDocument.java:1434: warning: [unchecked] unchecked conversion
        documentProperties = (Dictionary) f.get("documentProperties", null);
                             ^
  required: Dictionary<Object,Object>
  found: Dictionary