Documented the IllegalArgumentException thrown when the initial directory was invalid, and improved the exception description to be more precise and informative.
------------- Commit messages: - 8365938: FileChooser: Folder parameter must be a valid folder Changes: https://git.openjdk.org/jfx/pull/2101/files Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=2101&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8365938 Stats: 10 lines in 2 files changed: 6 ins; 0 del; 4 mod Patch: https://git.openjdk.org/jfx/pull/2101.diff Fetch: git fetch https://git.openjdk.org/jfx.git pull/2101/head:pull/2101 PR: https://git.openjdk.org/jfx/pull/2101
