RFR: JDK-8283087: Create a test or JDK-4715503

[Srinivas Mandalika]

Create a test or [JDK-4715503](https://bugs.openjdk.java.net/browse/JDK-4715503)

The getAccessibleContext method for JTable column header cells returns an
 AccessibleContext which cannot get the Bounding Rectangle for table header cells. The Bug causes problems with screen reader review mode.

The test added verifies that the are not exceptions and Bounding rectangles are returned for the Accessible Table Header Cells.

This review is for migrating tests from a closed test suite to open.

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Commit messages:
 - 8283087: Create a test or JDK-4715503

Changes: https://git.openjdk.java.net/jdk/pull/7807/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7807&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8283087
  Stats: 83 lines in 1 file changed: 83 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7807.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7807/head:pull/7807

PR: https://git.openjdk.java.net/jdk/pull/7807