Setup: Xvfb :1 -screen 0 1280x1024x24 DISPLAY=:1.0 openbox & Run: DISPLAY=:1.0 mach mochitest-browser Expected: A log of passes and failures with minimal noise. Actual: A log of passes and failures with a ton of messages about JavaScript failures in chrome://mochitests/content/browser/browser/base/content/test/newtab/head.js. I've attached a log for a single test showing examples. It's possible this is just due to running openbox and a different WM would be better... They start after browser_newtab_bug735987.js, which times out, if it makes any difference. Maybe the same cause of the timeout as bug 898317?

Nathan, try metacity instead of openbox. I use metacity and it seems to work for me. I also had similar problems - which forced me to abandon xvfb many months ago. This week I started to use Xephyr together with metacity, instead of xvfb, and it seems to work better. I had no issues.

Code was removed in bug 1433133 https://hg.mozilla.org/mozilla-central/rev/fc80dd3e4fae