Bug 1813716 - Encapsulate aboutwelcome container and make its ID more unique. r=omc-reviewers,fxview-reviewers,sfoster,jprickett

Differential Revision: https://phabricator.services.mozilla.com/D172493

browser/components/newtab/content-src/lib/aboutwelcome-utils.js

@@ -5,9 +5,10 @@
 // If the container has a "page" data attribute, then this is
 // a Spotlight modal or Feature Callout. Otherwise, this is
 // about:welcome and we should return the current page.
-const page = document.querySelector("#root.onboardingContainer[data-page]")
-  ? document.querySelector("#root[data-page]").dataset.page
-  : document.location.href;
+const page =
+  document.querySelector(
+    "#multi-stage-message-root.onboardingContainer[data-page]"
+  )?.dataset.page || document.location.href;
 
 export const AboutWelcomeUtils = {
   handleUserAction(action) {