[Caja] Fix global 'window' for ES53 case. (issue4252050)

[ihab . awad]

Reviewers: metaweta,



Please review this at http://codereview.appspot.com/4252050/

Affected files:
  M     src/com/google/caja/es53.js
  M     src/com/google/caja/plugin/domita.js
  M     tests/com/google/caja/plugin/es53-test-basic-functions-cajoled.html