diff -r 000000000000 -r 6474c204b198 dom/workers/test/test_bug883784.jsm
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/workers/test/test_bug883784.jsm	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,35 @@
+this.EXPORTED_SYMBOLS = ["Test"];
+
+this.Test = {
+  start: function(ok, is, finish) {
+    let worker = new ChromeWorker("jsm_url_worker.js");
+    worker.onmessage = function(event) {
+
+      if (event.data.type == 'finish') {
+        finish();
+      } else if (event.data.type == 'status') {
+        ok(event.data.status, event.data.msg);
+      } else if (event.data.type == 'url') {
+        var xhr = Components.classes["@mozilla.org/xmlextras/xmlhttprequest;1"]
+                  .createInstance(Components.interfaces.nsIXMLHttpRequest);
+        xhr.open('GET', event.data.url, false);
+        xhr.onreadystatechange = function() {
+          if (xhr.readyState == 4) {
+            ok(true, "Blob readable!");
+          }
+        }
+        xhr.send();
+      }
+    };
+
+    var self = this;
+    worker.onerror = function(event) {
+      is(event.target, worker);
+      ok(false, "Worker had an error: " + event.data);
+      self.worker.terminate();
+      finish();
+    };
+
+    worker.postMessage(0);
+  }
+};