test web page: Release blob when receiving a new one

index.html

@@ -6,9 +6,15 @@
     <script>
       document.addEventListener('DOMContentLoaded', () => {
 	  var img = document.getElementById("jpeg");
-	  var ws = new WebSocket("ws://{{.}}/video");
+	  var ws = new WebSocket("ws://{{.}}/jpeg");
+	  var oldurl;
 	  ws.onmessage = (event) => {
-	      img.src = URL.createObjectURL(event.data);
+	      var url = URL.createObjectURL(event.data);
+	      oldurl = img.src;
+	      img.src = url;
+	      if (oldurl != "") {
+		  URL.revokeObjectURL(oldurl);
+	      }
 	  };
       });
     </script>