Force intercept support for ooxml.

Change-Id: I065742bbe22f24169a99e33558399fe16c601238

oox/source/drawingml/chart/seriesconverter.cxx

@@ -436,6 +436,13 @@ void TrendlineConverter::convertFromModel( const Reference< XDataSeries >& rxDat
             aPropSet.setProperty( PROP_PolynomialDegree, mrModel.mnOrder );
             aPropSet.setProperty( PROP_MovingAveragePeriod, mrModel.mnPeriod );
 
+            // Intercept
+            sal_Bool hasIntercept = mrModel.mfIntercept.has();
+            aPropSet.setProperty( PROP_ForceIntercept, hasIntercept);
+            if (hasIntercept)
+                aPropSet.setProperty( PROP_InterceptValue,  mrModel.mfIntercept.get());
+
+            // Extrapolation
             if (mrModel.mfForward.has())
                 aPropSet.setProperty( PROP_ExtrapolateForward, mrModel.mfForward.get() );
             if (mrModel.mfBackward.has())

oox/source/token/properties.txt

@@ -185,6 +185,7 @@ FooterHeight
 FooterIsDynamicHeight
 FooterIsOn
 FooterIsShared
+ForceIntercept
 FormulaConvention
 FrameIsAutomaticHeight
 Function
@@ -238,6 +239,7 @@ ImageURL
 IncludeHiddenCells
 InputMessage
 InputTitle
+InterceptValue
 IsActive
 IsAdjustHeightEnabled
 IsCaseSensitive