diff -r 000000000000 -r 6474c204b198 toolkit/components/social/test/browser/worker_xhr.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/components/social/test/browser/worker_xhr.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,34 @@
+// Used to test XHR in the worker.
+onconnect = function(e) {
+  let port = e.ports[0];
+  let req;
+  try {
+    req = new XMLHttpRequest();
+  } catch(e) {
+    port.postMessage({topic: "done", result: "FAILED to create XHR object, " + e.toString() });
+  }
+  if (req === undefined) { // until bug 756173 is fixed...
+    port.postMessage({topic: "done", result: "FAILED to create XHR object"});
+    return;
+  }
+  // The test that uses this worker MUST use the same origin to load the worker.
+  // We fetch the test app manifest so we can check the data is what we expect.
+  let url = "https://example.com/browser/toolkit/components/social/test/browser/data.json";
+  req.open("GET", url, true);
+  req.onreadystatechange = function() {
+    if (req.readyState === 4) {
+      let ok = req.status == 200 && req.responseText.length > 0;
+      if (ok) {
+        // check we actually got something sane...
+        try {
+          let data = JSON.parse(req.responseText);
+          ok = "response" in data;
+        } catch(e) {
+          ok = e.toString();
+        }
+      }
+      port.postMessage({topic: "done", result: ok ? "ok" : "bad response"});
+    }
+  }
+  req.send(null);
+}