Fix reentrency of the QCSS engine.
Fix reentrency of the QCSS engine.

QTextDocument which is suposed to be reentrant may use the CSS Parser in
different threads.
The way the indexOfId was computed is not thread safe.
Insert the pre-computed value instead

Reviewed-by: Thierry

KDE/qt,radekp/qt,RLovelett/qt,igor-sfdc/qt-wk,KDE/qt,RLovelett/qt,RLovelett/qt,RLovelett/qt,pruiz/wkhtmltopdf-qt,radekp/qt,KDE/qt,RLovelett/qt,pruiz/wkhtmltopdf-qt,KDE/qt,radekp/qt,RLovelett/qt,igor-sfdc/qt-wk,igor-sfdc/qt-wk,radekp/qt,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,RLovelett/qt,igor-sfdc/qt-wk,radekp/qt,radekp/qt,igor-sfdc/qt-wk,KDE/qt,pruiz/wkhtmltopdf-qt,KDE/qt,igor-sfdc/qt-wk,radekp/qt,igor-sfdc/qt-wk,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,RLovelett/qt,radekp/qt,igor-sfdc/qt-wk,KDE/qt,pruiz/wkhtmltopdf-qt,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,radekp/qt,pruiz/wkhtmltopdf-qt,radekp/qt,RLovelett/qt,RLovelett/qt,RLovelett/qt,KDE/qt,igor-sfdc/qt-wk