diff -r 000000000000 -r 6474c204b198 browser/base/content/newtab/preloaderContent.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/base/content/newtab/preloaderContent.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,31 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+(function () { // bug 673569 workaround :(
+
+const ALLOW_BG_CAPTURES_MSG = "BrowserNewTabPreloader:allowBackgroundCaptures";
+
+addMessageListener(ALLOW_BG_CAPTURES_MSG, function onMsg(msg) {
+  removeMessageListener(ALLOW_BG_CAPTURES_MSG, onMsg);
+
+  if (content.document.readyState == "complete") {
+    setAllowBackgroundCaptures();
+    return;
+  }
+
+  // This is the case when preloading is disabled.
+  addEventListener("load", function onLoad(event) {
+    if (event.target == content.document) {
+      removeEventListener("load", onLoad, true);
+      setAllowBackgroundCaptures();
+    }
+  }, true);
+});
+
+function setAllowBackgroundCaptures() {
+  content.document.documentElement.setAttribute("allow-background-captures",
+                                                "true");
+}
+
+})();