<Swing Dev> RFR: 7124397: [macosx] JSpinner serialiazation - deserialization issue

[Sergey Bylokhov]

The serialization was broken because different listeners are leaked in the case of compound components. 
That listeners also caused memory leaks which were fixed by a few fixes here and there, and in jdk16 the serialization start to work fine. But I would like to contribute the test which will prove that serialization works fine.

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Commit messages:
 - Create SerializationTest.java

Changes: https://git.openjdk.java.net/jdk/pull/989/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=989&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-7124397
  Stats: 77 lines in 1 file changed: 77 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/989.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/989/head:pull/989

PR: https://git.openjdk.java.net/jdk/pull/989