tdf#113696 Add mimetype also to fallback graphic

Change-Id: I6eb7bb66aa688b5668d0eacd2ec7131bec2b6955
Reviewed-on: https://gerrit.libreoffice.org/45585Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Samuel Mehrbrodt <Samuel.Mehrbrodt@cib.de>
Reviewed-on: https://gerrit.libreoffice.org/45678Tested-by: Samuel Mehrbrodt <Samuel.Mehrbrodt@cib.de>

xmloff/source/draw/shapeexport.cxx

@@ -2393,6 +2393,14 @@ void XMLShapeExport::ImpExportGraphicObjectShape(
                     mrExport.AddAttribute(XML_NAMESPACE_XLINK, XML_SHOW, XML_EMBED );
                     mrExport.AddAttribute(XML_NAMESPACE_XLINK, XML_ACTUATE, XML_ONLOAD );
                 }
+
+                uno::Reference<io::XInputStream> xInputStream(
+                    mrExport.GetEmbeddedGraphicObjectStream(aReplacementUrl));
+                OUString aMimeType(
+                    comphelper::GraphicMimeTypeHelper::GetMimeTypeForImageStream(xInputStream));
+                if (!aMimeType.isEmpty())
+                    GetExport().AddAttribute(XML_NAMESPACE_LO_EXT, "mime-type", aMimeType);
+
                 SvXMLElementExport aOBJ(mrExport, XML_NAMESPACE_DRAW, XML_IMAGE, true, true);
 
                 // optional office:binary-data