In browser.xhtml browser chrome tests that use waitForNewWindow hang. This is because with browser.xhtml the focus/activate events can be triggered before the DOMContentLoaded event. Failing tests: browser/base/content/test/contextMenu/browser_contextmenu_linkopen.js browser/base/content/test/popups/browser_popupUI.js browser/components/sessionstore/test/browser_394759_behavior.js browser/components/extensions/test/browser/browser_ext_windows.js browser/base/content/test/general/browser_newWindowDrop.js browser/base/content/test/general/browser_new_http_window_opened_from_file_tab.js browser/components/privatebrowsing/test/browser/browser_privatebrowsing_newtab_from_popup.js browser/components/extensions/test/browser/test-oop-extensions/browser_ext_windows.js dom/tests/browser/browser_noopener.js toolkit/components/windowwatcher/test/browser_new_content_window_from_chrome_principal.js

In browser.xhtml the focus and activate events can fire before the DOMContentLoaded event.

Pushed by gijskruitbosch@gmail.com: https://hg.mozilla.org/integration/autoland/rev/1e422e5034f1 Handle different event order when waiting for window to open. r=Gijs