--- a/browser/components/extensions/ext-bookmarks.js
+++ b/browser/components/extensions/ext-bookmarks.js
@@ -5,17 +5,17 @@
 // The ext-* files are imported into the same scopes.
 /* import-globals-from ext-browserAction.js */
 
 XPCOMUtils.defineLazyModuleGetter(this, "PlacesUtils",
                                   "resource://gre/modules/PlacesUtils.jsm");
 
 let listenerCount = 0;
 
-function getTree(rootGuid, onlyChildren) {
+const getTree = (rootGuid, onlyChildren) => {
   function convert(node, parent) {
     let treenode = {
       id: node.guid,
       title: node.title || "",
       index: node.index,
       dateAdded: node.dateAdded / 1000,
     };
 
@@ -52,19 +52,19 @@ function getTree(rootGuid, onlyChildren)
       let children = root.children || [];
       return children.map(child => convert(child, root));
     }
     let treenode = convert(root, null);
     treenode.parentId = root.parentGuid;
     // It seems like the array always just contains the root node.
     return [treenode];
   }).catch(e => Promise.reject({message: e.message}));
-}
+};
 
-function convert(result) {
+const convertBookmarks = result => {
   let node = {
     id: result.guid,
     title: result.title || "",
     index: result.index,
     dateAdded: result.dateAdded.getTime(),
   };
 
   if (result.guid != PlacesUtils.bookmarks.rootGuid) {
@@ -73,17 +73,17 @@ function convert(result) {
 
   if (result.type == PlacesUtils.bookmarks.TYPE_BOOKMARK) {
     node.url = result.url.href; // Output is always URL object.
   } else {
     node.dateGroupModified = result.lastModified.getTime();
   }
 
   return node;
-}
+};
 
 let observer = {
   skipTags: true,
   skipDescendantsOnItemRemoval: true,
 
   onBeginUpdateBatch() {},
   onEndUpdateBatch() {},
 
@@ -158,45 +158,45 @@ let observer = {
       return;
     }
 
     this.emit("changed", {guid, info});
   },
 };
 EventEmitter.decorate(observer);
 
-function decrementListeners() {
+const decrementListeners = () => {
   listenerCount -= 1;
   if (!listenerCount) {
     PlacesUtils.bookmarks.removeObserver(observer);
   }
-}
+};
 
-function incrementListeners() {
+const incrementListeners = () => {
   listenerCount++;
   if (listenerCount == 1) {
     PlacesUtils.bookmarks.addObserver(observer);
   }
-}
+};
 
 this.bookmarks = class extends ExtensionAPI {
   getAPI(context) {
     return {
       bookmarks: {
         async get(idOrIdList) {
           let list = Array.isArray(idOrIdList) ? idOrIdList : [idOrIdList];
 
           try {
             let bookmarks = [];
             for (let id of list) {
               let bookmark = await PlacesUtils.bookmarks.fetch({guid: id});
               if (!bookmark) {
                 throw new Error("Bookmark not found");
               }
-              bookmarks.push(convert(bookmark));
+              bookmarks.push(convertBookmarks(bookmark));
             }
             return bookmarks;
           } catch (error) {
             return Promise.reject({message: error.message});
           }
         },
 
         getChildren: function(id) {
@@ -208,21 +208,21 @@ this.bookmarks = class extends Extension
           return getTree(PlacesUtils.bookmarks.rootGuid, false);
         },
 
         getSubTree: function(id) {
           return getTree(id, false);
         },
 
         search: function(query) {
-          return PlacesUtils.bookmarks.search(query).then(result => result.map(convert));
+          return PlacesUtils.bookmarks.search(query).then(result => result.map(convertBookmarks));
         },
 
         getRecent: function(numberOfItems) {
-          return PlacesUtils.bookmarks.getRecent(numberOfItems).then(result => result.map(convert));
+          return PlacesUtils.bookmarks.getRecent(numberOfItems).then(result => result.map(convertBookmarks));
         },
 
         create: function(bookmark) {
           let info = {
             title: bookmark.title || "",
           };
 
           // If url is NULL or missing, it will be a folder.
@@ -239,17 +239,17 @@ this.bookmarks = class extends Extension
 
           if (bookmark.parentId !== null) {
             info.parentGuid = bookmark.parentId;
           } else {
             info.parentGuid = PlacesUtils.bookmarks.unfiledGuid;
           }
 
           try {
-            return PlacesUtils.bookmarks.insert(info).then(convert)
+            return PlacesUtils.bookmarks.insert(info).then(convertBookmarks)
               .catch(error => Promise.reject({message: error.message}));
           } catch (e) {
             return Promise.reject({message: `Invalid bookmark: ${JSON.stringify(info)}`});
           }
         },
 
         move: function(id, destination) {
           let info = {
@@ -258,17 +258,17 @@ this.bookmarks = class extends Extension
 
           if (destination.parentId !== null) {
             info.parentGuid = destination.parentId;
           }
           info.index = (destination.index === null) ?
             PlacesUtils.bookmarks.DEFAULT_INDEX : destination.index;
 
           try {
-            return PlacesUtils.bookmarks.update(info).then(convert)
+            return PlacesUtils.bookmarks.update(info).then(convertBookmarks)
               .catch(error => Promise.reject({message: error.message}));
           } catch (e) {
             return Promise.reject({message: `Invalid bookmark: ${JSON.stringify(info)}`});
           }
         },
 
         update: function(id, changes) {
           let info = {
@@ -278,17 +278,17 @@ this.bookmarks = class extends Extension
           if (changes.title !== null) {
             info.title = changes.title;
           }
           if (changes.url !== null) {
             info.url = changes.url;
           }
 
           try {
-            return PlacesUtils.bookmarks.update(info).then(convert)
+            return PlacesUtils.bookmarks.update(info).then(convertBookmarks)
               .catch(error => Promise.reject({message: error.message}));
           } catch (e) {
             return Promise.reject({message: `Invalid bookmark: ${JSON.stringify(info)}`});
           }
         },
 
         remove: function(id) {
           let info = {

--- a/toolkit/components/extensions/ext-cookies.js
+++ b/toolkit/components/extensions/ext-cookies.js
@@ -5,17 +5,17 @@
 
 XPCOMUtils.defineLazyModuleGetter(this, "ContextualIdentityService",
                                   "resource://gre/modules/ContextualIdentityService.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "NetUtil",
                                   "resource://gre/modules/NetUtil.jsm");
 
 /* globals DEFAULT_STORE, PRIVATE_STORE */
 
-function convert({cookie, isPrivate}) {
+const convertCookie = ({cookie, isPrivate}) => {
   let result = {
     name: cookie.name,
     value: cookie.value,
     domain: cookie.host,
     hostOnly: !cookie.isDomain,
     path: cookie.path,
     secure: cookie.isSecure,
     httpOnly: cookie.isHttpOnly,
@@ -30,25 +30,25 @@ function convert({cookie, isPrivate}) {
     result.storeId = getCookieStoreIdForContainer(cookie.originAttributes.userContextId);
   } else if (cookie.originAttributes.privateBrowsingId || isPrivate) {
     result.storeId = PRIVATE_STORE;
   } else {
     result.storeId = DEFAULT_STORE;
   }
 
   return result;
-}
+};
 
-function isSubdomain(otherDomain, baseDomain) {
+const isSubdomain = (otherDomain, baseDomain) => {
   return otherDomain == baseDomain || otherDomain.endsWith("." + baseDomain);
-}
+};
 
 // Checks that the given extension has permission to set the given cookie for
 // the given URI.
-function checkSetCookiePermissions(extension, uri, cookie) {
+const checkSetCookiePermissions = (extension, uri, cookie) => {
   // Permission checks:
   //
   //  - If the extension does not have permissions for the specified
   //    URL, it cannot set cookies for it.
   //
   //  - If the specified URL could not set the given cookie, neither can
   //    the extension.
   //
@@ -124,19 +124,19 @@ function checkSetCookiePermissions(exten
   // domain cookie.
   cookie.host = "." + cookie.host;
 
   // We don't do any significant checking of path permissions. RFC2109
   // suggests we only allow sites to add cookies for sub-paths, similar to
   // same origin policy enforcement, but no-one implements this.
 
   return true;
-}
+};
 
-function* query(detailsIn, props, context) {
+const query = function* (detailsIn, props, context) {
   // Different callers want to filter on different properties. |props|
   // tells us which ones they're interested in.
   let details = {};
   props.forEach(property => {
     if (detailsIn[property] !== null) {
       details[property] = detailsIn[property];
     }
   });
@@ -263,36 +263,36 @@ function* query(detailsIn, props, contex
   }
 
   while (enumerator.hasMoreElements()) {
     let cookie = enumerator.getNext().QueryInterface(Ci.nsICookie2);
     if (matches(cookie)) {
       yield {cookie, isPrivate, storeId};
     }
   }
-}
+};
 
 this.cookies = class extends ExtensionAPI {
   getAPI(context) {
     let {extension} = context;
     let self = {
       cookies: {
         get: function(details) {
           // FIXME: We don't sort by length of path and creation time.
           for (let cookie of query(details, ["url", "name", "storeId"], context)) {
-            return Promise.resolve(convert(cookie));
+            return Promise.resolve(convertCookie(cookie));
           }
 
           // Found no match.
           return Promise.resolve(null);
         },
 
         getAll: function(details) {
           let allowed = ["url", "name", "domain", "path", "secure", "session", "storeId"];
-          let result = Array.from(query(details, allowed, context), convert);
+          let result = Array.from(query(details, allowed, context), convertCookie);
 
           return Promise.resolve(result);
         },
 
         set: function(details) {
           let uri = NetUtil.newURI(details.url).QueryInterface(Ci.nsIURL);
 
           let path;
@@ -379,17 +379,17 @@ this.cookies = class extends ExtensionAP
         },
 
         onChanged: new SingletonEventManager(context, "cookies.onChanged", fire => {
           let observer = (subject, topic, data) => {
             let notify = (removed, cookie, cause) => {
               cookie.QueryInterface(Ci.nsICookie2);
 
               if (extension.whiteListedHosts.matchesCookie(cookie)) {
-                fire.async({removed, cookie: convert({cookie, isPrivate: topic == "private-cookie-changed"}), cause});
+                fire.async({removed, cookie: convertCookie({cookie, isPrivate: topic == "private-cookie-changed"}), cause});
               }
             };
 
             // We do our best effort here to map the incompatible states.
             switch (data) {
               case "deleted":
                 notify(true, subject, "explicit");
                 break;