sw: DOCX export: eliminate chart numbering non-determinism

... that was causing test failures on some but not all platforms.

(cherry picked from commit c56e0858)
(cherry picked from commit 2263a59a)

Change-Id: I0d04cd6e540ea2693a3ec8511d615a9b0fecf456
Reviewed-on: https://gerrit.libreoffice.org/20757Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Miklos Vajna <vmiklos@collabora.co.uk>

sw/source/filter/ww8/docxattributeoutput.cxx

@@ -4411,10 +4411,9 @@ void DocxAttributeOutput::WritePostponedChart()
             FSEND );
 
         OString aRelId;
-        static sal_Int32 nChartCount = 0;
-        nChartCount++;
+        m_nChartCount++;
         uno::Reference< frame::XModel > xModel( xChartDoc, uno::UNO_QUERY );
-        aRelId = m_rExport.OutputChart( xModel, nChartCount, m_pSerializer );
+        aRelId = m_rExport.OutputChart( xModel, m_nChartCount, m_pSerializer );
 
         m_pSerializer->singleElementNS( XML_c, XML_chart,
             FSNS( XML_xmlns, XML_c ), "http://schemas.openxmlformats.org/drawingml/2006/chart",
@@ -8410,6 +8409,7 @@ DocxAttributeOutput::DocxAttributeOutput( DocxExport &rExport, FSHelperPtr pSeri
       m_startedHyperlink( false ),
       m_nHyperLinkCount(0),
       m_nFieldsInHyperlink( 0 ),
+      m_nChartCount(0),
       m_postponedChart( NULL ),
       pendingPlaceholder( NULL ),
       m_postitFieldsMaxId( 0 ),

sw/source/filter/ww8/docxattributeoutput.hxx

@@ -861,6 +861,8 @@ private:
     std::unique_ptr< std::list<PostponedOLE> > m_pPostponedOLEs;
 
     std::vector<const SwOLENode*> m_aPostponedMaths;
+    /// count charts consistently for unit tests
+    unsigned int m_nChartCount;
     const SdrObject* m_postponedChart;
     Size m_postponedChartSize;
     std::vector<const SdrObject*> m_aPostponedFormControls;