[Caja] Add tests to browser-tests to check the differences between visited and unvisited link styles

[mikesamuel]

Reviewers: ihab.awad,

Description:
Creates a visited link and an unvisited link and compares the computed
styles.

Please review this at http://codereview.appspot.com/63131

Affected files:
  M     tests/com/google/caja/browser-expectations.html
  M     third_party/js/jsunit/2.2/jsUnitCore.js