Bug 1700201 - Fix branding on csv detail import report page. r=sfoster

Differential Revision: https://phabricator.services.mozilla.com/D109502

browser/components/aboutlogins/AboutLoginsChild.jsm

@@ -113,6 +113,11 @@ class AboutLoginsChild extends JSWindowActorChild {
       }
       case "AboutLoginsImportReportInit": {
         this.sendAsyncMessage("AboutLogins:ImportReportInit");
+        let documentElement = this.document.documentElement;
+        documentElement.classList.toggle(
+          "official-branding",
+          AppConstants.MOZILLA_OFFICIAL
+        );
         break;
       }
       case "AboutLoginsCopyLoginDetail": {