RFR: 8245183: Two fxml unit tests log warnings about deprecated escape sequences

[Kevin Rushforth]

On Thu, 21 May 2020 15:48:34 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> Issue : https://bugs.openjdk.java.net/browse/JDK-8245183
>> Fix : Added a message to the test saying these are expected warnings. Refer JBS comments for more details.
>
> Marked as reviewed by kcr (Lead).

While running the FXML tests, I see two more test warnings due to the fact that Nashorn has been deprecated (for quite
some time now). Now that Nashorn has been removed in JDK 15, we will need to address this by replacing the tests with
something that doesn't use Nashorn. I filed [JDK-8245568](https://bugs.openjdk.java.net/browse/JDK-8245568) as a
follow-up issue to track this.

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PR: https://git.openjdk.java.net/jfx/pull/225