The security warning window feature is used when the "java.awt.Window" object is insecure. That feature is tied to the Applets and Security manager, both are marked as deprecated for removal already:
 - Applets are deprecated by the https://bugs.openjdk.org/browse/JDK-8189198
 - Security Manager is deprecated by the https://bugs.openjdk.org/browse/JDK-8266459

As a result, we can deprecate the " security warning window" as well, and then later delete its implementation by making the public API noop.

The security warning window feature has a few parts:
 - The java.awt.Window.getWarningString() method
 - The "awt.appletWarning" system property
 - The heavy-weight implementation of small warning window for any frames on each platform