RFR: 6777156: GTK JFileChooser can show /../../../.. in combobox and selection textarea

[Abhishek Kumar]

When a user selects ../ from directory list in GTK FileChooser continuosly, it leads to '../../../.....' in combobox and selection textarea even though it the current directory is at root level.

Fix for the issue is to check if current directory is root then don't process the selection of ' ../ '.

Test case has been added and checked in CI pipeline. Link is attached in JBS.

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Commit messages:
 - JFileChooser combobox and selection textarea displayed directory list fix

Changes: https://git.openjdk.org/jdk/pull/10390/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10390&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-6777156
  Stats: 113 lines in 2 files changed: 113 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/10390.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10390/head:pull/10390

PR: https://git.openjdk.org/jdk/pull/10390