Separated from bug 1442465. The following tests were waiting for the promise returned by BrowserTestUtils.removeTab, but the promise is removed in bug 1442465: * browser/components/originattributes/test/browser/browser_favicon_firstParty.js * browser/components/originattributes/test/browser/browser_favicon_userContextId.js * browser/components/privatebrowsing/test/browser/browser_privatebrowsing_favicon.js What those tests actually should do is wait for some event after closing a tab, before continuing the next test, to ensure that the network request for the first tab is not observed in the next test. In bug 1442465 patch, I just made them to wait for the next event tick, and looks like it works, but it would be better specifically wait for some event.

actually this doesn't block.