1747085 - BrowserTestUtils should have a utility to conceal the main window

Status: NEW

(Testing :: General, enhancement)

Description

[Julien Wajsberg [:julienw]]

In some tests we may need to conceal the main window to simulate specific scenarios, eg only private windows being opened.

This could look like this:

function concealMainWindow() {
  info("Concealing main window.");
  let oldWinType = document.documentElement.getAttribute("windowtype");
  // Check if we've already done this to allow calling multiple times:
  if (oldWinType != "navigator:testrunner") {
    // Make the main test window not count as a browser window any longer
    document.documentElement.setAttribute("windowtype", "navigator:testrunner");
    BrowserWindowTracker.untrackForTestsOnly(window);

    registerCleanupFunction(() => {
      info("Unconcealing the main window in the cleanup phase.");
      BrowserWindowTracker.track(window);
      document.documentElement.setAttribute("windowtype", oldWinType);
    });
  }
}

And then we could remove existing code in tests such as the one in browser/base/content/test/utilityOverlay/browser_openWebLinkIn.js (not landed yet) or https://searchfox.org/mozilla-central/rev/b605f01915c5704a55e9f485101b7be7d20a55df/browser/base/content/test/popups/browser_popup_close_main_window.js#6