RFR: 8295298: Automate javax/swing/JFileChooser/FileViewNPETest.java [v2]

[Alexey Ivanov]

> The automated test follows the instructions of the manual test that was added in #10485.
> 
> Instead of selecting the parent folder from the **Look in** combo box, it calls `setCurrentDirectory` directly with the parent of the path which is not traversable. Thus, the current directory of the file chooser is set to `null`.
> 
> As the second step, the test finds the combo box and re-selects the currently selected element. Without the fix for [JDK-6616245](https://bugs.openjdk.org/browse/JDK-6616245), `NullPointerException` is thrown and the test fails; with the fix applied, the original folder is selected and the test passes.
> 
> @mrserb and @TejeshR13, please, take a look.

Alexey Ivanov has updated the pull request incrementally with one additional commit since the last revision:

  Convert asserts to explicit checks

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/10801/files
  - new: https://git.openjdk.org/jdk/pull/10801/files/c878454b..478f2070

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10801&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10801&range=00-01

  Stats: 8 lines in 1 file changed: 3 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/10801.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10801/head:pull/10801

PR: https://git.openjdk.org/jdk/pull/10801