JDK-8097121 removed all references to sun.misc.BASE64Decoder and sun.misc.BASE64Encoder except for modules/javafx.web/src/android/**

The following file is still using the internal sun.misc.BASE64Encoder class:

modules/javafx.web/src/android/java/javafx/scene/web/WebEngine.java [1]

The sun.misc base64 encoder classes were removed from JDK 9, so this file cannot possibly compile using an unmodified JDK. It should be replaced by using the public java.util.Base64 class.

[1] https://github.com/openjdk/jfx/blob/c77c2335856a967907aaacc9546f44943c069add/modules/javafx.web/src/android/java/javafx/scene/web/WebEngine.java#L478