Bug 1864445: Add text zoom only warning r=dholbert,fluent-reviewers,desktop-theme-reviewers,dao,mconley,flod

Differential Revision: https://phabricator.services.mozilla.com/D196116

browser/components/preferences/main.js

@@ -969,6 +969,8 @@ var gMainPane = {
 
     setEventListener("zoomText", "command", function () {
       win.ZoomManager.toggleZoom();
+      document.getElementById("text-zoom-override-warning").hidden =
+        !document.getElementById("zoomText").checked;
     });
 
     let zoomValues = win.ZoomManager.zoomValues.map(a => {
@@ -991,7 +993,8 @@ var gMainPane = {
 
     let checkbox = document.getElementById("zoomText");
     checkbox.checked = !win.ZoomManager.useFullZoom;
-
+    document.getElementById("text-zoom-override-warning").hidden =
+      !checkbox.checked;
     document.getElementById("zoomBox").hidden = false;
   },