--- a/browser/components/preferences/aboutPermissions.js
+++ b/browser/components/preferences/aboutPermissions.js
@@ -326,18 +326,22 @@ var PermissionDefaults = {
       return this.DENY;
     }
     return this.UNKNOWN;
   },
   set push(aValue) {
     let value = (aValue != this.DENY);
     Services.prefs.setBoolPref("dom.push.enabled", value);
   },
-  get camera() this.UNKNOWN,
-  get microphone() this.UNKNOWN
+  get camera() {
+    return this.UNKNOWN;
+  },
+  get microphone() {
+    return this.UNKNOWN;
+  }
 };
 
 /**
  * AboutPermissions manages the about:permissions page.
  */
 var AboutPermissions = {
   /**
    * Number of sites to return from the places database.

--- a/browser/components/preferences/in-content/applications.js
+++ b/browser/components/preferences/in-content/applications.js
@@ -398,17 +398,17 @@ HandlerInfoWrapper.prototype = {
                                           this.type,
                                           false);
   },
 
   enablePluginType: function() {
     var disabledPluginTypes = this._getDisabledPluginTypes();
 
     var type = this.type;
-    disabledPluginTypes = disabledPluginTypes.filter(function(v) v != type);
+    disabledPluginTypes = disabledPluginTypes.filter(v => v != type);
 
     this._prefSvc.setCharPref(PREF_DISABLED_PLUGIN_TYPES,
                               disabledPluginTypes.join(","));
 
     // Update the category manager so existing browser windows update.
     this._categoryMgr.
       addCategoryEntry("Gecko-Content-Viewers",
                        this.type,
@@ -1544,17 +1544,17 @@ var gApplicationsPane = {
         menu.selectedItem = internalMenuItem;
         break;
       case Ci.nsIHandlerInfo.useSystemDefault:
         menu.selectedItem = defaultMenuItem;
         break;
       case Ci.nsIHandlerInfo.useHelperApp:
         if (preferredApp)
           menu.selectedItem = 
-            possibleAppMenuItems.filter(function(v) v.handlerApp.equals(preferredApp))[0];
+            possibleAppMenuItems.filter(v => v.handlerApp.equals(preferredApp))[0];
         break;
       case kActionUsePlugin:
         menu.selectedItem = pluginMenuItem;
         break;
       case Ci.nsIHandlerInfo.saveToDisk:
         menu.selectedItem = saveMenuItem;
         break;
     }

--- a/browser/components/preferences/in-content/main.js
+++ b/browser/components/preferences/in-content/main.js
@@ -293,17 +293,19 @@ var gMainPane = {
    * Sets the home page to the current displayed page (or frontmost tab, if the
    * most recent browser window contains multiple tabs), updating preference
    * window UI to reflect this.
    */
   setHomePageToCurrent: function ()
   {
     let homePage = document.getElementById("browser.startup.homepage");
     let tabs = this._getTabsForHomePage();
-    function getTabURI(t) t.linkedBrowser.currentURI.spec;
+    function getTabURI(t) {
+      return t.linkedBrowser.currentURI.spec;
+    }
 
     // FIXME Bug 244192: using dangerous "|" joiner!
     if (tabs.length)
       homePage.value = tabs.map(getTabURI).join("|");
   },
 
   /**
    * Displays a dialog in which the user can select a bookmark to use as home

--- a/browser/components/preferences/in-content/privacy.js
+++ b/browser/components/preferences/in-content/privacy.js
@@ -174,18 +174,17 @@ var gPrivacyPane = {
   },
 
   /**
    * Initialize the history mode menulist based on the privacy preferences
    */
   initializeHistoryMode: function PPP_initializeHistoryMode()
   {
     let mode;
-    let getVal = function (aPref)
-      document.getElementById(aPref).value;
+    let getVal = aPref => document.getElementById(aPref).value;
 
     if (this._checkDefaultValues(this.prefsForDefault)) {
       if (getVal("browser.privatebrowsing.autostart"))
         mode = "dontremember";
       else
         mode = "remember";
     }
     else

--- a/browser/components/preferences/in-content/search.js
+++ b/browser/components/preferences/in-content/search.js
@@ -313,17 +313,17 @@ function onDragEngineStart(event) {
 function EngineStore() {
   let pref = document.getElementById("browser.search.hiddenOneOffs").value;
   this.hiddenList = pref ? pref.split(",") : [];
 
   this._engines = Services.search.getVisibleEngines().map(this._cloneEngine, this);
   this._defaultEngines = Services.search.getDefaultEngines().map(this._cloneEngine, this);
 
   // check if we need to disable the restore defaults button
-  var someHidden = this._defaultEngines.some(function (e) e.hidden);
+  var someHidden = this._defaultEngines.some(e => e.hidden);
   gSearchPane.showRestoreDefaults(someHidden);
 }
 EngineStore.prototype = {
   _engines: null,
   _defaultEngines: null,
 
   get engines() {
     return this._engines;

--- a/browser/components/preferences/translation.js
+++ b/browser/components/preferences/translation.js
@@ -20,58 +20,82 @@ const kLanguagesPref = "browser.translat
 function Tree(aId, aData)
 {
   this._data = aData;
   this._tree = document.getElementById(aId);
   this._tree.view = this;
 }
 
 Tree.prototype = {
-  get boxObject() this._tree.treeBoxObject,
-  get isEmpty() !this._data.length,
-  get hasSelection() this.selection.count > 0,
+  get boxObject() {
+    return this._tree.treeBoxObject;
+  },
+  get isEmpty() {
+    return !this._data.length;
+  },
+  get hasSelection() {
+    return this.selection.count > 0;
+  },
   getSelectedItems: function() {
     let result = [];
 
     let rc = this.selection.getRangeCount();
     for (let i = 0; i < rc; ++i) {
       let min = {}, max = {};
       this.selection.getRangeAt(i, min, max);
       for (let j = min.value; j <= max.value; ++j)
         result.push(this._data[j]);
     }
 
     return result;
   },
 
   // nsITreeView implementation
-  get rowCount() this._data.length,
-  getCellText: function (aRow, aColumn) this._data[aRow],
-  isSeparator: function(aIndex) false,
-  isSorted: function() false,
-  isContainer: function(aIndex) false,
+  get rowCount() {
+    return this._data.length;
+  },
+  getCellText: function (aRow, aColumn) {
+    return this._data[aRow];
+  },
+  isSeparator: function(aIndex) {
+    return false;
+  },
+  isSorted: function() {
+    return false;
+  },
+  isContainer: function(aIndex) {
+    return false;
+  },
   setTree: function(aTree) {},
   getImageSrc: function(aRow, aColumn) {},
   getProgressMode: function(aRow, aColumn) {},
   getCellValue: function(aRow, aColumn) {},
   cycleHeader: function(column) {},
-  getRowProperties: function(row) "",
-  getColumnProperties: function(column) "",
-  getCellProperties: function(row, column) "",
+  getRowProperties: function(row) {
+    return "";
+  },
+  getColumnProperties: function(column) {
+    return "";
+  },
+  getCellProperties: function(row, column) {
+    return "";
+  },
   QueryInterface: XPCOMUtils.generateQI([Ci.nsITreeView])
 };
 
 function Lang(aCode)
 {
   this.langCode = aCode;
   this._label = gLangBundle.GetStringFromName(aCode);
 }
 
 Lang.prototype = {
-  toString: function() this._label
+  toString: function() {
+    return this._label;
+  }
 }
 
 var gTranslationExceptions = {
   onLoad: function() {
     if (this._siteTree) {
       // Re-using an open dialog, clear the old observers.
       this.uninit();
     }