--- a/browser/components/customizableui/test/browser_synced_tabs_menu.js
+++ b/browser/components/customizableui/test/browser_synced_tabs_menu.js
@@ -86,17 +86,17 @@ async function openPrefsFromMenuPanel(ex
   let subpanel = document.getElementById(expectedPanelId);
   ok(!subpanel.hidden, "sync setup element is visible");
 
   // Find and click the "setup" button.
   let setupButton = subpanel.querySelector(".PanelUI-remotetabs-prefs-button");
   setupButton.click();
 
   await new Promise(resolve => {
-    let handler = async(e) => {
+    let handler = async (e) => {
       if (e.originalTarget != gBrowser.selectedBrowser.contentDocument ||
           e.target.location.href == "about:blank") {
         info("Skipping spurious 'load' event for " + e.target.location.href);
         return;
       }
       gBrowser.selectedBrowser.removeEventListener("load", handler, true);
       resolve();
     };

--- a/browser/components/extensions/test/browser/browser_ext_browsingData_pluginData.js
+++ b/browser/components/extensions/test/browser/browser_ext_browsingData_pluginData.js
@@ -50,17 +50,17 @@ function stored(needles) {
     return true;
   }
 
   return false;
 }
 
 add_task(async function testPluginData() {
   function background() {
-    browser.test.onMessage.addListener(async(msg, options) => {
+    browser.test.onMessage.addListener(async (msg, options) => {
       if (msg == "removePluginData") {
         await browser.browsingData.removePluginData(options);
       } else {
         await browser.browsingData.remove(options, {pluginData: true});
       }
       browser.test.sendMessage("pluginDataRemoved");
     });
   }

--- a/browser/components/uitour/UITour.jsm
+++ b/browser/components/uitour/UITour.jsm
@@ -1614,17 +1614,17 @@ this.UITour = {
         break;
       default:
         log.error("setConfiguration: Unknown configuration requested: " + aConfiguration);
         break;
     }
   },
 
   getAppInfo(aMessageManager, aWindow, aCallbackID) {
-    (async() => {
+    (async () => {
       let props = ["defaultUpdateChannel", "version"];
       let appinfo = {};
       props.forEach(property => appinfo[property] = Services.appinfo[property]);
 
       // Identifier of the partner repack, as stored in preference "distribution.id"
       // and included in Firefox and other update pings. Note this is not the same as
       // Services.appinfo.distributionID (value of MOZ_DISTRIBUTION_ID is set at build time).
       let distribution =

--- a/toolkit/components/payments/test/browser/browser_show_dialog.js
+++ b/toolkit/components/payments/test/browser/browser_show_dialog.js
@@ -13,17 +13,17 @@ add_task(async function test_show_abort_
 
     // get a reference to the UI dialog and the requestId
     let win = await getPaymentWidget();
     let requestId = paymentUISrv.requestIdForWindow(win);
     ok(requestId, "requestId should be defined");
     is(win.closed, false, "dialog should not be closed");
 
     // abort the payment request
-    ContentTask.spawn(browser, null, async() => content.rq.abort());
+    ContentTask.spawn(browser, null, async () => content.rq.abort());
     await BrowserTestUtils.waitForCondition(() => win.closed, "dialog should be closed");
   });
 });
 
 add_task(async function test_show_manualAbort_dialog() {
   await BrowserTestUtils.withNewTab({
     gBrowser,
     url: BLANK_PAGE_URL,