1. Enable the pref browser.tabs.remote.autostart. 2. Restart the browser. 3. Navigate to https://www.khronos.org/registry/webgl/sdk/demos/webkit/SpiritBox.html Expected: A spinning textured cube should render. Observed: The WebGL canvas element does not appear on the page. Also, it seems that the page gets constantly reflow'ed, see the web console. Another example page here https://dl.dropboxusercontent.com/u/40949268/emcc/10kCubes/10kCubes.html , which in addition to not displaying anything, is showing a graph of the performance impact.

Regression window(m-i): Good: https://hg.mozilla.org/integration/mozilla-inbound/rev/5f286e259379 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Firefox/31.0 ID:20140401004332 Bad: https://hg.mozilla.org/integration/mozilla-inbound/rev/d1f8ac35bdd4 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Firefox/31.0 ID:20140401005432 Pushlog: http://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=5f286e259379&tochange=d1f8ac35bdd4 Regressed by: Bug 990338

Not tracking. Electrolysis is not enabled by default.