RFR: 8315317: Add test for JDK-8262518 [v2]

[Prasanta Sadhukhan]

> Added automated test for 8262518:SwingNode.setContent does not close previous content, resulting in memory leak

Prasanta Sadhukhan has updated the pull request incrementally with one additional commit since the last revision:

  Better failure detection

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Changes:
  - all: https://git.openjdk.org/jfx/pull/1228/files
  - new: https://git.openjdk.org/jfx/pull/1228/files/ac0205a0..bf7623a3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1228&range=01
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1228&range=00-01

  Stats: 14 lines in 1 file changed: 3 ins; 9 del; 2 mod
  Patch: https://git.openjdk.org/jfx/pull/1228.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1228/head:pull/1228

PR: https://git.openjdk.org/jfx/pull/1228