Uncovered when landing real performance actor. Originally, we would wait for perf connection during toolbox startup during testing, so it'd be available, and we don't get race conditions when tearing down. Looks like some jetpack tests don't have gDevTools.testing on (why would they?), so was running into this. Have a much cleaner solution now. https://treeherder.mozilla.org/#/jobs?repo=fx-team&revision=4e11c910454f TEST-UNEXPECTED-FAIL | jetpack-package/addon-sdk/source/test/test-dev-panel.js.test Panel API | There was an uncaught Promise rejection: Error: Connection closed, pending request to server1.conn0.performanceActor21, type connect failed TEST-UNEXPECTED-FAIL | jetpack-package/addon-sdk/source/test/test-dev-panel.js.test createView panel | There was an uncaught Promise rejection: Error: Connection closed, pending request to server1.conn4.performanceActor21, type connect failed TEST-UNEXPECTED-FAIL | jetpack-package/addon-sdk/source/test/test-dev-panel.js.test viewFor panel | There was an uncaught Promise rejection: Error: Connection closed, pending request to server1.conn6.performanceActor21, type connect failed

Comment on attachment 8646100 [details] [diff] [review] 1193110-perf-toolbox.patch Review of attachment 8646100 [details] [diff] [review]: ----------------------------------------------------------------- ::: browser/devtools/framework/toolbox.js @@ +1983,3 @@ > } > > + this._performanceConnection = promise.defer(); Maybe this should be `_performanceFront`, since that's your create function's name on the next line?

Turns out lots of tests just close a tab without waiting for toolbox destruction, so we still need the DevToolsUtils.testing flag unfortunately, but the jetpack tests do wait for this, so this'll fix that anyway. https://treeherder.mozilla.org/#/jobs?repo=try&revision=ecc243a43b9a