[Patch] Allow non-default file formats with native file chooser

[simon04]

The native file chooser has been added in #10024.

Since NativeFileChooser#getChoosableFileFilters always returns an empty array, in saving does not permit non-default file formats.

To reproduce:

1. Enable native file chooser
2. New data layer, draw some lines
3. Save as
4. Input foobar.gpx
5. File is saved as foobar.gpx.osm in OSM format

Build-Date:2016-08-18 18:38:37
Revision:10840
Is-Local-Build:true

Identification: JOSM/1.5 (10840 SVN en) Linux Arch Linux
Memory Usage: 589 MB / 3504 MB (194 MB allocated, but free)
Java version: 1.8.0_102-b14, Oracle Corporation, OpenJDK 64-Bit Server VM
VM arguments: [-agentlib:jdwp=transport=dt_socket,address=127.0.0.1:41665,suspend=y,server=n, -Djosm.home=<josm.pref>, -javaagent:/usr/share/intellijidea-ce/plugins/Groovy/lib/agent/gragent.jar, -Dfile.encoding=UTF-8]
Program arguments: [--set=use.native.file.dialog=true, --set=expert=true, --set=remotecontrol.enabled=true, --set=debug.edt-checker.enable=true, --set=dialog.dynamic.buttons=false, --set=iso.dates=true]
Dataset consistency test: No problems found

[Don-vip]

If I remember correctly it did not work at all because of a lot of Java bugs (those in comments). Have they been solved since?

[Don-vip]

JDK bugs are still there but I confirm your patch works as expected on Windows too.

[simon04]

In 11004/josm:

fix #13414 - Allow non-default file formats with native file chooser

[simon04]

Milestone renamed