Remove context menus from mutators and flyouts.

git-svn-id: http://blockly.googlecode.com/svn/trunk@1684 c400ca83-b69d-9dd7-9705-49c6b8615e23
A simpler way to remove context menus from mutators and flyouts.

git-svn-id: http://blockly.googlecode.com/svn/trunk@1685 c400ca83-b69d-9dd7-9705-49c6b8615e23