STR: - Use a recent fx-team build (I don't know when this started, but I see it today, wasn't seeing it yesterday, at least I didn't notice it). - Open the inspector on any page. - Move your mouse over the rule-view area. - Watch the browser console or terminal output. Errors are being logged at each mousemove: console.error: isValidHoverTarget rejected with an unexpected reason: console.error: undefined

A candidate could be bug 1022765.

Oops, I forgot to ensure the other usages of Tooltip conformed to startTogglingOnHover exceptations (the callback should reject `false`, otherwise it is considered as an error and logged). May be we could ease that to any falsy rejection value? https://treeherder.mozilla.org/#/jobs?repo=try&revision=976a9a88de35

Comment on attachment 8595983 [details] [diff] [review] patch Review of attachment 8595983 [details] [diff] [review]: ----------------------------------------------------------------- Thanks Alex for picking that up quickly. Also my bad for not having seen this coming when reviewing the other bug.