RFR: 8274383 JNI call of getAccessibleSelection on a wrong thread

[Artem Semenov]

[ComboBoxAccessibility accessibilityValue] defines the getAccessibleSelection method on the AccessibleContext class, however the call should go through CAccessibility so that it is executed on the Event Dispatch thread.

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Commit messages:
 - 8274383 JNI call of getAccessibleSelection on a wrong thread

Changes: https://git.openjdk.java.net/jdk/pull/5735/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5735&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8274383
  Stats: 16 lines in 1 file changed: 12 ins; 1 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5735.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5735/head:pull/5735

PR: https://git.openjdk.java.net/jdk/pull/5735