add javadoc

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1916150 13f79535-47bb-0310-9956-ffa450edef68

poi-ooxml/src/main/java/org/apache/poi/xdgf/usermodel/section/geometry/PolyLineTo.java

@@ -24,6 +24,10 @@ import org.apache.poi.xdgf.usermodel.XDGFShape;
 import com.microsoft.schemas.office.visio.x2012.main.CellType;
 import com.microsoft.schemas.office.visio.x2012.main.RowType;
 
+/**
+ * Represents a polyline vertex in a shape's geometry.
+ * Until POI 5.2.6, this class not was not properly implemented and was throwing an exception.
+ */
 public class PolyLineTo implements GeometryRow {
 
     private static final String POLYLINE_FORMULA_PREFIX = "POLYLINE(";