Bug 846856: TEST-UNEXPECTED-FAIL | tests/test-window-utils-private-browsing.testSettingActiveWindowIgnoresPrivateWindow | Correct active window [1]

It looks like getMostRecentBrowserWindow() doesn't return the window focused when the "focus" event occurs, but instead sometime afterward..
Merge pull request #835 from erikvold/846856

Fix Bug 846856 - TEST-UNEXPECTED-FAIL | tests/test-window-utils-private-browsing.testSettingActiveWindowIgnoresPrivateWindow | Correct active window [1] r=@ochameau