Bug 1541706 - attempt to fix intermittent browser_privatebrowsing.js, r=mixedpuppy

Differential Revision: https://phabricator.services.mozilla.com/D42663

--HG--
extra : moz-landing-system : lando

toolkit/mozapps/extensions/test/xpinstall/browser_privatebrowsing.js

@@ -22,7 +22,6 @@ function check_channel(subject) {
 // ----------------------------------------------------------------------------
 // Tests we send the right cookies when installing through an InstallTrigger call
 let gPrivateWin;
-let gPopupShown;
 async function test() {
   waitForExplicitFinish(); // have to call this ourselves because we're async.
   Harness.installConfirmCallback = confirm_install;
@@ -57,10 +56,6 @@ async function test() {
     gPrivateWin.gBrowser,
     TESTROOT + "installtrigger.html?" + triggers
   );
-  gPopupShown = BrowserTestUtils.waitForEvent(
-    gPrivateWin.PanelUI.notificationPanel,
-    "popupshown"
-  );
 }
 
 function confirm_install(panel) {
@@ -102,16 +97,17 @@ const finish_test = async function(count) {
   is(results.return, "true", "installTrigger should have claimed success");
   is(results.status, "0", "Callback should have seen a success");
 
-  // Explicitly click the "OK" button to avoid the panel reopening in the other window once this
-  // window closes (see also bug 1535069):
-  await gPopupShown;
-  gPrivateWin.PanelUI.notificationPanel
-    .querySelector("popupnotification[popupid=addon-installed]")
-    .button.click();
+  await TestUtils.waitForCondition(() =>
+    gPrivateWin.AppMenuNotifications._notifications.some(
+      n => n.id == "addon-installed"
+    )
+  );
+  // Explicitly remove the notification to avoid the panel reopening in the
+  // other window once this window closes (see also bug 1535069):
+  gPrivateWin.AppMenuNotifications.removeNotification("addon-installed");
 
   // Now finish the test:
   await BrowserTestUtils.closeWindow(gPrivateWin);
   Harness.finish(gPrivateWin);
   gPrivateWin = null;
-  gPopupShown = null;
 };

toolkit/mozapps/extensions/test/xpinstall/head.js

@@ -179,6 +179,7 @@ var Harness = {
     // that which fixes the rest of the tests.  Since no test
     // here cares about this panel, we just need it to close.
     win.PanelUI.notificationPanel.hidePopup();
+    win.AppMenuNotifications.removeNotification("addon-installed");
     delete this._boundWin;
     finish();
   },