DevTools uses the chrome-only insertAnonymousContent[1] API to insert things like the highlighters that appear over elements when using the inspector. With Stylo, such content does not show up and doesn't seem to receive events. The leads to failures like: (These tests only run in --disable-e10s mode.) * devtools/server/tests/browser/browser_canvasframe_helper_03.js[2] TEST-UNEXPECTED-FAIL | devtools/server/tests/browser/browser_canvasframe_helper_03.js | The mousedown event was handled once on the element - Got 0, expected 1 Similar failures also show up for: * devtools/server/tests/browser/browser_canvasframe_helper_04.js * devtools/server/tests/browser/browser_canvasframe_helper_05.js * devtools/server/tests/browser/browser_canvasframe_helper_06.js [1]: http://searchfox.org/mozilla-central/rev/1a054419976437d0778a2b89be1b00207a744e94/dom/webidl/Document.webidl#422 [2]: https://treeherder.mozilla.org/logviewer.html#?job_id=105301401&repo=try&lineNumber=3561

These tests seem to work for me locally. Do they still fail for you Ryan?

(In reply to Cameron McCormack (:heycam) from comment #1) > These tests seem to work for me locally. Do they still fail for you Ryan? They seem to work locally for me as well, and a newer try run agrees. Great! :)