Part 1 of reimplementing DevMode JSO implementation to remove the need for global state.
Add SingleJsoImpl annotation
http://gwt-code-reviews.appspot.com/473801
Patch by: bobv
Review by: scottb


git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@8246 8db76d5a-ed1c-0410-87a9-c151d255dfc7