I would suggest adding a test to TextBoxTests. You may also look at other subclasses of ValueBoxBase to see if their tests should be updated for this change.
Putting things in a test obviously guard against a regression, but they also document a particular behavior as being intentional. When it comes to the handling of whitespace in the DOM, browsers are so inconsistent that it's best to document (through a test) whenever you do some normalization. http://gwt-code-reviews.appspot.com/738801/show -- http://groups.google.com/group/Google-Web-Toolkit-Contributors
