Bug 1490729 - Ensure that we send variation=0 for the TP UI on about:privatebrowsing. r=Gijs

Differential Revision: https://phabricator.services.mozilla.com/D5680

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

browser/components/privatebrowsing/content/aboutPrivateBrowsing.js

@@ -67,7 +67,7 @@ document.addEventListener("DOMContentLoaded", function() {
   let introURL = RPMGetFormatURLPref("privacy.trackingprotection.introURL");
   // If the CB UI is enabled, tell the tour page to show a different variation
   // that is updated to reflect the CB control center UI.
-  let variation = contentBlockingUIEnabled ? "?variation=1" : "";
+  let variation = "?variation=" + (contentBlockingUIEnabled ? "1" : "0");
 
   document.getElementById("startTour").setAttribute("href", introURL + variation);
 

browser/components/privatebrowsing/test/browser/browser_privatebrowsing_about.js

@@ -70,7 +70,7 @@ add_task(async function test_links() {
 
   await testLinkOpensUrl({ win, tab,
     elementId: "startTour",
-    expectedUrl: "https://example.com/tour",
+    expectedUrl: "https://example.com/tour?variation=0",
   });
 
   await BrowserTestUtils.closeWindow(win);