RFR: 8282402: Create a regression test for JDK-4666101

[Manukumar V S]

Create a regression test for [JDK-4666101](https://bugs.openjdk.java.net/browse/JDK-4666101).

DESCRIPTION OF THE ACTUAL PROBLEM :
In a JEditorPane, the down arrow has no effect after you add text on a line preceding a blank line.

Testing:
As the original issue was reported in JDK 1.4.0 and it was fixed in JDK 1.4.2, I have verified the working of this test in those Java versions and the results are as follows:

Java 1.4.0 -> Test Failed.
$ ./j2sdk1.4.0/bin/java JEditorBugWin
Caret Updated : 3
Test Failed, Down Arrow Key Not Functional, expected caret position is 5, but actual is 4


Java 1.4.2 -> Test Passed.
$ ./j2sdk1.4.2/bin/java JEditorBugWin
Caret Updated : 5
Test Passed, Down Arrow Key Functional

-------------

Commit messages:
 - 8282402: Create a regression test for JDK-4666101

Changes: https://git.openjdk.java.net/jdk/pull/7623/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7623&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8282402
  Stats: 186 lines in 1 file changed: 186 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7623.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7623/head:pull/7623

PR: https://git.openjdk.java.net/jdk/pull/7623