fix for download webms?

src/websrv.js

@@ -193,6 +193,7 @@ function Websrv(tlib) {
                 'Connection':'close',
                 'Content-Type':contentType,
                 'Content-Length':end - start,
+                'Content-Length':stat.size,
                 'Content-Range':'bytes '+start+'-'+end+'/'+stat.size,
                 'Transfer-Encoding':'chunked'
               });