https://tbpl.mozilla.org/php/getParsedLog.php?id=33223498&tree=Mozilla-Central b2g_ubuntu32_vm mozilla-central opt test gaia-integration on 2014-01-18 04:43:42 PST for push b3c08e6fa790 slave: tst-linux32-spot-377 05:16:26 INFO - TEST-START | using the gallery menu should let you select images 05:16:46 INFO - TEST-UNEXPECTED-FAIL | using the gallery menu "before each" hook 05:16:46 INFO - undefined 05:16:46 INFO - TEST-UNEXPECTED-FAIL | using the gallery menu "after each" hook 05:16:46 INFO - undefined ... 05:17:06 INFO - 1) using the gallery menu "before each" hook: 05:17:06 INFO - Error: timeout of 20000ms exceeded 05:17:06 INFO - at null.<anonymous> (/builds/slave/test/gaia/node_modules/mocha/lib/runnable.js:165:14) 05:17:06 INFO - at Timer.listOnTimeout [as ontimeout] (timers.js:110:15) 05:17:06 INFO - 2) using the gallery menu "after each" hook: 05:17:06 INFO - TypeError: Cannot read property 'deleteSession' of null 05:17:06 INFO - at Object.executeHook (/builds/slave/test/gaia/node_modules/marionette-client/lib/marionette/client.js:354:32) 05:17:06 INFO - at Object.Client.runHook (/builds/slave/test/gaia/node_modules/marionette-client/lib/marionette/client.js:378:7) 05:17:06 INFO - at Object.destroySession [as deleteSession] (/builds/slave/test/gaia/node_modules/marionette-client/lib/marionette/client.js:757:12) 05:17:06 INFO - at Context.<anonymous> (/builds/slave/test/gaia/node_modules/marionette-js-runner/lib/runtime/hostmanager.js:102:14) 05:17:06 INFO - at Hook.Runnable.run (/builds/slave/test/gaia/node_modules/mocha/lib/runnable.js:194:15) 05:17:06 INFO - at next (/builds/slave/test/gaia/node_modules/mocha/lib/runner.js:257:10) 05:17:06 INFO - at Object._onImmediate (/builds/slave/test/gaia/node_modules/mocha/lib/runner.js:274:5) 05:17:06 INFO - at processImmediate [as _immediateCallback] (timers.js:330:15)

Appears this is part of an infrastructure bug, let's track it in bug 1005707.