--- a/toolkit/content/l20n-chrome-xul.js
+++ b/toolkit/content/l20n-chrome-xul.js
@@ -169,20 +169,18 @@ class LocalizationObserver {
           break;
         case 'childList':
           for (let addedNode of mutation.addedNodes) {
             if (addedNode.nodeType === addedNode.ELEMENT_NODE) {
               if (addedNode.childElementCount) {
                 this.getTranslatables(addedNode).forEach(
                   targets.add.bind(targets)
                 );
-              } else {
-                if (addedNode.hasAttribute('data-l10n-id')) {
-                  targets.add(addedNode);
-                }
+              } else if (addedNode.hasAttribute('data-l10n-id')) {
+                targets.add(addedNode);
               }
             }
           }
           break;
       }
     }
 
     if (targets.size === 0) {

--- a/toolkit/content/l20n-perf-monitor.js
+++ b/toolkit/content/l20n-perf-monitor.js
@@ -1,42 +1,54 @@
 {
 let winUtils = window.QueryInterface(Components.interfaces.nsIInterfaceRequestor)
                      .getInterface(Components.interfaces.nsIDOMWindowUtils);
 
 let iTransactionId;
 
 document.addEventListener('MozBeforeLayout', function(evt) {
-  if (evt.target !== document) return false;
+  if (evt.target !== document) {
+    return false;
+  }
+
   iTransactionId = winUtils.lastTransactionId;
   performance.mark(`mozBeforeLayout[tID=${iTransactionId}]`);
+  return true;
 }, true);
 
 function logFirstPaint(event) {
   let afterInteractive = false;
   if (event.transactionId > iTransactionId) {
     afterInteractive = true;
   }
-  let info = event.transactionId === iTransactionId ? 'at interactive':
-    event.transactionId > iTransactionId ? 'after interactive' : 'before interactive';
+
+  let info;
+  if (event.transactionId === iTransactionId) {
+    info = 'at interactive';
+  } else if (event.transactionId > iTransactionId) {
+    info = 'after interactive';
+  } else {
+    info = 'before interactive';
+  }
+
   performance.mark(`Paint for tID: ${event.transactionId} (${info})`);
   if (afterInteractive) {
     window.removeEventListener('MozAfterPaint', logFirstPaint, true);
   }
 }
 
-  const timingEvents = [
-    'domLoading',
-    'domInteractive',
-    'domContentLoadedEventStart',
-    'domContentLoadedEventEnd',
-    'domComplete',
-    'loadEventStart',
-    'loadEventEnd',
-  ];
+const timingEvents = [
+  'domLoading',
+  'domInteractive',
+  'domContentLoadedEventStart',
+  'domContentLoadedEventEnd',
+  'domComplete',
+  'loadEventStart',
+  'loadEventEnd',
+];
 
 setTimeout(() => {
   console.log('--- Performance.Timing ---');
   console.log(`navigationStart: ${performance.timing.navigationStart}`);
   timingEvents.forEach(eventName => {
     if (performance.timing[eventName]) {
       console.log(`${eventName}: ${performance.timing[eventName] - performance.timing.navigationStart}`);
     }

--- a/toolkit/modules/L10nRegistry.jsm
+++ b/toolkit/modules/L10nRegistry.jsm
@@ -47,17 +47,17 @@ function load(path) {
       }
     });
 
     req.addEventListener('error', reject);
     req.addEventListener('timeout', reject);
 
     try {
       req.send(null);
-    } catch(e) {
+    } catch (e) {
       reject(e);
     }
   }, true);
 }
 
 class FileSource extends Source {
   constructor(name, prePath) {
     super(name);
@@ -86,26 +86,23 @@ function prioritizeLocales(defaultLang, 
 
   supportedLocales.add(defaultLang);
   return supportedLocales;
 }
 
 function getRPermuts(array, size, initialStuff = []) {
   if (initialStuff.length >= size) {
     return initialStuff;
-  } else {
-    return array.map(elem => {
-      return getRPermuts(array, size, initialStuff.concat(elem));
-    }).reduce((a, b) => {
-      if (b.every(e => typeof e === 'string')) {
-        return [a, b];
-      }
-      return a.concat(b);
-    });
   }
+
+  return array.map(elem => {
+    return getRPermuts(array, size, initialStuff.concat(elem));
+  }).reduce(
+    (a, b) => b.every(e => typeof e === 'string') ? [a, b] : a.concat(b)
+  );
 }
 
 function fetchFirstBundle(bundles) {
   // worst-case scenario: the list of bundles to return to the client is empty
   if (bundles.length === 0) {
     return bundles;
   }
 
@@ -203,19 +200,19 @@ const L10nRegistry = {
 
   fetchResource(source, resId, lang) {
     const cacheId = `${resId}-${lang}-${source}`;
 
     if (cache.has(cacheId)) {
       let val = cache.get(cacheId);
       if (val === null) {
         return Promise.reject();
-      } else {
-        return Promise.resolve(val);
       }
+
+      return Promise.resolve(val);
     }
 
     return sources.get(source).loadResource(resId, lang).then(data => {
       cache.set(cacheId, data);
       return data;
     }, err => {
       cache.set(cacheId, null);
       return Promise.reject();