sendBeacon should throw a TypeError on bad URLs.

third_party/WebKit/LayoutTests/fast/events/resources/message-port-iframe.html

+<script src="../../../resources/gc.js"></script>
 <script>
-function gc()
-{
-    if (window.GCController)
-        return GCController.collect();
-
-    for (var i = 0; i < 10000; i++) { // > force garbage collection (FF requires about 9K allocations before a collect)
-        var s = new String("abc");
-    }
-}
-
 var port;
 function onMessage(evt) {
     if (evt.data == "ping")
         port.postMessage("pong");
     else if (evt.data == "newPort")
         evt.ports[0].postMessage("yo");
     else if (evt.data == "newConversation")
         if (evt.origin == "")
             evt.ports[0].postMessage("hey");
         else
             alert("Incorrect security origin in conversation: '" + evt.origin + "'.");
     else if (/alert.+/.test(evt.data))
         alert(evt.data.substr(6));
     else if (evt.data == "freeze")
         while (1) {}
     else if (evt.data == "closePort")
         this.close();
     else if (evt.data == "closeFrame") {
         frameElement.parentNode.removeChild(frameElement);
         gc();
     }
 }
 
 window.addEventListener("message", function(evt) {
     port = evt.ports[0];
     port.onmessage = onMessage;
     port.start();
 }, false);
 </script>