diff -r 000000000000 -r 6474c204b198 toolkit/components/thumbnails/test/browser_thumbnails_bg_timeout.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/components/thumbnails/test/browser_thumbnails_bg_timeout.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,19 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+function runTests() {
+  let url = bgTestPageURL({ wait: 30000 });
+  ok(!thumbnailExists(url), "Thumbnail should not be cached already.");
+  let numCalls = 0;
+  BackgroundPageThumbs.capture(url, {
+    timeout: 0,
+    onDone: function onDone(capturedURL) {
+      is(capturedURL, url, "Captured URL should be URL passed to capture");
+      is(numCalls++, 0, "onDone should be called only once");
+      ok(!thumbnailExists(url),
+         "Capture timed out so thumbnail should not be cached");
+      next();
+    },
+  });
+  yield true;
+}