Setting extra diagnostics would call updateDocument which would in turn
trigger another scan.

Change-Id: I3810a380cdf716a12767d94ff82dc30f8ae3954d
Reviewed-on: http://codereview.qt.nokia.com/3917


Reviewed-by: Roberto Raggi <roberto.raggi@nokia.com>
Reviewed-by: Leandro T. C. Melo <leandro.melo@nokia.com>