Merge trunk r9187 - introduce DirectionalTextHelper.

Patch by: jat
Review by: tomerigo

Original public review at http://gwt-code-reviews.appspot.com/901801


git-svn-id: https://google-web-toolkit.googlecode.com/svn/releases/2.1@9311 8db76d5a-ed1c-0410-87a9-c151d255dfc7