Clarify EditorDriver behavior with combinations of Editor mix-in interfaces through brute-force testing.
Patch by: bobv
Review by: rjrjr

Review at http://gwt-code-reviews.appspot.com/840801


git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@8710 8db76d5a-ed1c-0410-87a9-c151d255dfc7