diff -r 000000000000 -r 6474c204b198 browser/base/content/test/general/browser_bug479408.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/base/content/test/general/browser_bug479408.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,17 @@
+function test() {
+  waitForExplicitFinish();
+  let tab = gBrowser.selectedTab = gBrowser.addTab(
+    "http://mochi.test:8888/browser/browser/base/content/test/general/browser_bug479408_sample.html");
+  
+  gBrowser.addEventListener("DOMLinkAdded", function(aEvent) {
+    gBrowser.removeEventListener("DOMLinkAdded", arguments.callee, true);
+    
+    executeSoon(function() {
+      ok(!tab.linkedBrowser.engines,
+         "the subframe's search engine wasn't detected");
+      
+      gBrowser.removeTab(tab);
+      finish();
+    });
+  }, true);
+}