RFR: JDK-8282778: Create a regression test for JDK-4699544 [v4]

[Srinivas Mandalika]

> Create a regression test for JDK-4699544
> 
> The subclass of javax.swing.JRootPane (AccessibleJRootPane) that implements the accessibility interface javax.accessibility.AccessibleComponent is derived from java.awt.AccessibleAWTComponent, which returns null for getAccessibleAt() because a component does not necessarily have childs.
> 
> The root pane always has a content pane child, so getAccessibleAt() should be overwritten by AccessibleJRootPane appropriately.
> The test added verifies the same.
> This review is for migrating tests from a closed test suite to open.

Srinivas Mandalika has updated the pull request incrementally with one additional commit since the last revision:

  Review Comments Fixed: removed redundant class variables

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7739/files
  - new: https://git.openjdk.java.net/jdk/pull/7739/files/bcc3bd6c..15bc3210

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7739&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7739&range=02-03

  Stats: 4 lines in 1 file changed: 0 ins; 2 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7739.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7739/head:pull/7739

PR: https://git.openjdk.java.net/jdk/pull/7739