fixup e199e1b3 for non-e10s FF: moar timeouts!

.eslintrc

@@ -37,6 +37,7 @@ globals:
   saveStyleSafe: false
   sessionStorageHash: false
   download: false
+  doTimeout: false
   # localization.js
   template: false
   t: false

backup/fileSaveLoad.js

@@ -329,14 +329,16 @@ $('#file-all-styles').onclick = () => {
           tag: 'iframe',
           style: 'width: 0; height: 0; position: fixed; opacity: 0;'.replace(/;/g, '!important;'),
         }));
-        setTimeout(() => {
+        doTimeout().then(() => {
           link = iframe.contentDocument.importNode(link, true);
           iframe.contentDocument.body.appendChild(link);
-          link.dispatchEvent(new MouseEvent('click'));
+        })
-          setTimeout(() => {
+        .then(doTimeout)
+        .then(() => link.dispatchEvent(new MouseEvent('click')))
+        .then(doTimeout(1000))
+        .then(() => {
           URL.revokeObjectURL(objectURL);
           iframe.remove();
-          }, 1000);
         });
       }
     });

messaging.js

@@ -359,3 +359,10 @@ function download(url) {
     xhr.send(query);
   });
 }
+
+
+function doTimeout(ms = 0, ...args) {
+  return ms > 0
+    ? () => new Promise(resolve => setTimeout(resolve, ms, ...args))
+    : new Promise(resolve => setTimeout(resolve, 0, ...args));
+}