<AWT Dev> [9] Review Request: 8039567 Duplicated code in DataTransferer

[Petr Pchelko]

Hello AWT team.

Please review a simple cleanup fix for the issue:
https://bugs.openjdk.java.net/browse/JDK-8039567
The fix is available here:
http://cr.openjdk.java.net/~pchelko/9/8039567/webrev/

1. The getBestCharsetForTextFormat is duplicated 3 times in the code.
2. Caching of the default Charset in DataTransferer does not make sense as it's already cached in the Charset class itself.
Adding more references to the nio.Charset is not a problem since it's used in this class anyway and we cannot break this
dependency.

With best regards. Petr.