<AWT Dev> RFR: 8264299: Create implementation of native accessibility peer for ScrollPane and ScrollBar Java Accessibility roles

[Pankaj Bansal]

Create implementation of native accessibility peer for ScrollPane and ScrollBar Java Accessibility roles.

There are no direct protocols for these two roles and there is no protocol in list of role based protocols defined by Apple Accessibility API, which can be used for these roles directly. So ScrollAreaAccessibility and ScrollBarAccessibility classes do not implement any of the role based protocols in this list. https://developer.apple.com/library/archive/documentation/Accessibility/Conceptual/AccessibilityMacOSX/ImplementingAccessibilityforCustomControls.html. 

By looking at the current implementation of ScrollAreaAccessibility class in JavaComponentAccessibility and the complete list of properties and methods which can be used for any NSAccessibility class listed in https://developer.apple.com/documentation/appkit/nsaccessibility, custom implementation of ScrollAreaAccessibility and ScrollBarAccessibility is created.

I have tested these implementations by running ScrollPane demo in SwingSet2 and scrollPane demo here https://docs.oracle.com/javase/tutorial/uiswing/components/scrollpane.html. The Voice Over behaviour is consistent with the old implementation and user can navigate and interact with the ScrollArea children hierarchy as expected.

The old ScrollAreaAccessibility class in JavaComponentAccessibility is renamed to ScrollAreaAccessibility_Old as this was causing compiler errors. Please let me know if there is a better way to handle this.
Also, some constants defined in JavaComponentAccessibility.m have been moved to JavaComponentAccessibility.h to avoid duplication in ScrollAreaAccessibility.

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Commit messages:
 - Add ScrollBar Accessibility
 - remove logs
 - Add functions to get ScrollBars from ScrollArea children
 - 8264299: Create implementation of native accessibility peer for ScrollPane  Java Accessibility role

Changes: https://git.openjdk.java.net/jdk/pull/3794/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3794&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8264299
  Stats: 255 lines in 7 files changed: 244 ins; 7 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3794.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3794/head:pull/3794

PR: https://git.openjdk.java.net/jdk/pull/3794