RFR: 8287740 NSAccessibilityShowMenuAction not working for text editors

[Artem Semenov]

The NSAccessibilityShouMinuAction action does not show the menu for the text element. 
Steps to reproduce: 
1. redefine the accessible context with the addition of the toggle popup action; 
2. run on macOS with VoiceOver enabled; 
3. try to call the context menu in the editor by pressing vo+shift+m.

@azuev-java please review.

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Commit messages:
 - 8287740 NSAccessibilityShowMenuAction not working for text editors

Changes: https://git.openjdk.java.net/jdk/pull/8997/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8997&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8287740
  Stats: 106 lines in 2 files changed: 97 ins; 6 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8997.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8997/head:pull/8997

PR: https://git.openjdk.java.net/jdk/pull/8997