diff -r 000000000000 -r 6474c204b198 dom/encoding/test/worker_helper.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/encoding/test/worker_helper.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,48 @@
+/*
+ * worker_helper.js
+ * bug 764234 tests
+*/
+function runTestInWorker(files) {
+  function workerRun() {
+    var tests = [];
+    var asserts;
+    test = function(func, msg) {
+      asserts = [];
+      tests.push({asserts: asserts, msg: msg});
+    }
+    assert_equals = function(result, expected, msg) {
+      asserts.push(["assert_equals", result, expected, msg]);
+    };
+    assert_true = function(condition, msg) {
+      asserts.push(["assert_true", condition, msg]);
+    };
+    assert_unreached = function(condition, msg) {
+      asserts.push(["assert_unreached", condition, msg]);
+    };
+    onmessage = function(event) {
+      importScripts.apply(self, event.data);
+      runTest();
+      postMessage(tests);
+    };
+  }
+
+  var url = URL.createObjectURL(new Blob([
+    runTest.toString(), "\n\n",
+    "(", workerRun.toString(), ")();"
+  ]));
+  var worker = new Worker(url);
+  var base = location.toString().replace(/\/[^\/]*$/,"/");
+  worker.postMessage(files.map(function(f) { return base + f; }));
+  worker.onmessage = function(event) {
+    URL.revokeObjectURL(url);
+    event.data.forEach(function(t) {
+      test(function() {
+        t.asserts.forEach(function(a) {
+          func = a.shift();
+          self[func].apply(self, a);
+        });
+      }, "worker " + t.msg);
+    });
+    done();
+  };
+}