enable promo banner

app/capabilities.js

@@ -93,6 +93,10 @@ export default async function getCapabilities() {
   const share =
     typeof navigator.share === 'function' && LOCALE.startsWith('en'); // en until strings merge
 
+  const standalone =
+    window.matchMedia('(display-mode: standalone)').matches ||
+    navigator.standalone;
+
   return {
     account,
     crypto,
@@ -101,6 +105,7 @@ export default async function getCapabilities() {
     streamDownload:
       nativeStreams && serviceWorker && browserName() !== 'safari',
     multifile: nativeStreams || polyStreams,
-    share
+    share,
+    standalone
   };
 }

app/ui/body.js

@@ -4,7 +4,15 @@ const Header = require('./header');
 const Footer = require('./footer');
 
 function banner(state) {
-  if (state.promo && !state.route.startsWith('/unsupported/')) {
+  if (state.layout) {
+    return; // server side
+  }
+  const show =
+    !state.capabilities.standalone &&
+    !/firefox/i.test(navigator.userAgent) &&
+    document.querySelector('html').lang.startsWith('en') &&
+    !state.route.startsWith('/unsupported/');
+  if (show) {
     return state.cache(Promo, 'promo').render();
   }
 }

app/ui/promo.js

@@ -27,7 +27,8 @@ class Promo extends Component {
             <a
               class="text-blue"
               href="https://www.mozilla.org/firefox/new/?utm_campaign=send-acquisition&utm_medium=referral&utm_source=send.firefox.com"
-              >Download Firefox now ≫</a
+            >
+              Download Firefox now ≫</a
             >
           </span>
         </div>