diff --git a/browser/base/content/browser.js b/browser/base/content/browser.js
index 366852f66129..ab5596e757fd 100755
--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -224,38 +224,54 @@ if (AppConstants.platform != "macosx") {
   ["gNavigatorBundle",    "bundle_browser"]
 ].forEach(function(elementGlobal) {
   var [name, id] = elementGlobal;
-  window.__defineGetter__(name, function() {
-    var element = document.getElementById(id);
-    if (!element)
-      return null;
-    delete window[name];
-    return window[name] = element;
-  });
-  window.__defineSetter__(name, function(val) {
-    delete window[name];
-    return window[name] = val;
+  Object.defineProperty(window, name, {
+    configurable: true,
+    enumerable: true,
+    get() {
+      var element = document.getElementById(id);
+      if (!element)
+        return null;
+      delete window[name];
+      return window[name] = element;
+    },
+    set(val) {
+      delete window[name];
+      return window[name] = val;
+    },
   });
 });
 
 // Smart getter for the findbar.  If you don't wish to force the creation of
 // the findbar, check gFindBarInitialized first.
 
-this.__defineGetter__("gFindBar", function() {
-  return window.gBrowser.getFindBar();
+Object.defineProperty(this, "gFindBar", {
+  configurable: true,
+  enumerable: true,
+  get() {
+    return window.gBrowser.getFindBar();
+  },
 });
 
-this.__defineGetter__("gFindBarInitialized", function() {
-  return window.gBrowser.isFindBarInitialized();
+Object.defineProperty(this, "gFindBarInitialized", {
+  configurable: true,
+  enumerable: true,
+  get() {
+    return window.gBrowser.isFindBarInitialized();
+  },
 });
 
-this.__defineGetter__("AddonManager", function() {
-  let tmp = {};
-  Cu.import("resource://gre/modules/AddonManager.jsm", tmp);
-  return this.AddonManager = tmp.AddonManager;
-});
-this.__defineSetter__("AddonManager", function(val) {
-  delete this.AddonManager;
-  return this.AddonManager = val;
+Object.defineProperty(this, "AddonManager", {
+  configurable: true,
+  enumerable: true,
+  get() {
+    let tmp = {};
+    Cu.import("resource://gre/modules/AddonManager.jsm", tmp);
+    return this.AddonManager = tmp.AddonManager;
+  },
+  set(val) {
+    delete this.AddonManager;
+    return this.AddonManager = val;
+  },
 });
 
 
diff --git a/browser/base/content/utilityOverlay.js b/browser/base/content/utilityOverlay.js
index ec4e13d095d2..4e014bb71557 100644
--- a/browser/base/content/utilityOverlay.js
+++ b/browser/base/content/utilityOverlay.js
@@ -18,13 +18,17 @@ XPCOMUtils.defineLazyServiceGetter(this, "aboutNewTabService",
                                    "@mozilla.org/browser/aboutnewtab-service;1",
                                    "nsIAboutNewTabService");
 
-this.__defineGetter__("BROWSER_NEW_TAB_URL", () => {
-  if (PrivateBrowsingUtils.isWindowPrivate(window) &&
-      !PrivateBrowsingUtils.permanentPrivateBrowsing &&
-      !aboutNewTabService.overridden) {
-    return "about:privatebrowsing";
-  }
-  return aboutNewTabService.newTabURL;
+Object.defineProperty(this, "BROWSER_NEW_TAB_URL", {
+  configurable: true,
+  enumerable: true,
+  get() {
+    if (PrivateBrowsingUtils.isWindowPrivate(window) &&
+        !PrivateBrowsingUtils.permanentPrivateBrowsing &&
+        !aboutNewTabService.overridden) {
+      return "about:privatebrowsing";
+    }
+    return aboutNewTabService.newTabURL;
+  },
 });
 
 var TAB_DROP_TYPE = "application/x-moz-tabbrowser-tab";
diff --git a/toolkit/components/viewsource/content/viewSource.js b/toolkit/components/viewsource/content/viewSource.js
index 2acfa055fe2a..f7213fce7012 100644
--- a/toolkit/components/viewsource/content/viewSource.js
+++ b/toolkit/components/viewsource/content/viewSource.js
@@ -27,12 +27,16 @@ XPCOMUtils.defineLazyModuleGetter(this, "Deprecated",
   ["gViewSourceBundle", "viewSourceBundle"],
   ["gContextMenu",      "viewSourceContextMenu"]
 ].forEach(function([name, id]) {
-  window.__defineGetter__(name, function() {
-    var element = document.getElementById(id);
-    if (!element)
-      return null;
-    delete window[name];
-    return window[name] = element;
+  Object.defineProperty(window, name, {
+    configurable: true,
+    enumerable: true,
+    get() {
+      var element = document.getElementById(id);
+      if (!element)
+        return null;
+      delete window[name];
+      return window[name] = element;
+    },
   });
 });
 
@@ -779,14 +783,18 @@ function getBrowser() {
   return gBrowser;
 }
 
-this.__defineGetter__("gPageLoader", function() {
-  var webnav = viewSourceChrome.webNav;
-  if (!webnav)
-    return null;
-  delete this.gPageLoader;
-  this.gPageLoader = (webnav instanceof Ci.nsIWebPageDescriptor) ? webnav
-                                                                 : null;
-  return this.gPageLoader;
+Object.defineProperty(this, "gPageLoader", {
+  configurable: true,
+  enumerable: true,
+  get() {
+    var webnav = viewSourceChrome.webNav;
+    if (!webnav)
+      return null;
+    delete this.gPageLoader;
+    this.gPageLoader = (webnav instanceof Ci.nsIWebPageDescriptor) ? webnav
+                                                                   : null;
+    return this.gPageLoader;
+  },
 });
 
 // Strips the |view-source:| for internalSave()
@@ -800,11 +808,15 @@ function ViewSourceSavePage() {
 // Below are old deprecated functions and variables left behind for
 // compatibility reasons. These will be removed soon via bug 1159293.
 
-this.__defineGetter__("gLastLineFound", function() {
-  Deprecated.warning("gLastLineFound is deprecated - please use " +
-                     "viewSourceChrome.lastLineFound instead.",
-                     "https://developer.mozilla.org/en-US/Add-ons/Code_snippets/View_Source_for_XUL_Applications");
-  return viewSourceChrome.lastLineFound;
+Object.defineProperty(this, "gLastLineFound", {
+  configurable: true,
+  enumerable: true,
+  get() {
+    Deprecated.warning("gLastLineFound is deprecated - please use " +
+                       "viewSourceChrome.lastLineFound instead.",
+                       "https://developer.mozilla.org/en-US/Add-ons/Code_snippets/View_Source_for_XUL_Applications");
+    return viewSourceChrome.lastLineFound;
+  },
 });
 
 function onLoadViewSource() {
diff --git a/toolkit/content/globalOverlay.js b/toolkit/content/globalOverlay.js
index dc849627947e..ae50c33d8b58 100644
--- a/toolkit/content/globalOverlay.js
+++ b/toolkit/content/globalOverlay.js
@@ -147,9 +147,13 @@ function setTooltipText(aID, aTooltipText) {
     element.setAttribute("tooltiptext", aTooltipText);
 }
 
-this.__defineGetter__("NS_ASSERT", function() {
-  delete this.NS_ASSERT;
-  var tmpScope = {};
-  Components.utils.import("resource://gre/modules/debug.js", tmpScope);
-  return this.NS_ASSERT = tmpScope.NS_ASSERT;
+Object.defineProperty(this, "NS_ASSERT", {
+  configurable: true,
+  enumerable: true,
+  get() {
+    delete this.NS_ASSERT;
+    var tmpScope = {};
+    Components.utils.import("resource://gre/modules/debug.js", tmpScope);
+    return this.NS_ASSERT = tmpScope.NS_ASSERT;
+  },
 });
diff --git a/toolkit/mozapps/downloads/DownloadUtils.jsm b/toolkit/mozapps/downloads/DownloadUtils.jsm
index 83e837e353b5..952198e76566 100644
--- a/toolkit/mozapps/downloads/DownloadUtils.jsm
+++ b/toolkit/mozapps/downloads/DownloadUtils.jsm
@@ -49,9 +49,13 @@ XPCOMUtils.defineLazyModuleGetter(this, "PluralForm",
 
 const MS_PER_DAY = 24 * 60 * 60 * 1000;
 
-this.__defineGetter__("gDecimalSymbol", function() {
+Object.defineProperty(this, "gDecimalSymbol", {
+  configurable: true,
+  enumerable: true,
+  get() {
     delete this.gDecimalSymbol;
       return this.gDecimalSymbol = Number(5.4).toLocaleString().match(/\D/);
+  },
 });
 
 var localeNumberFormatCache = new Map();
@@ -95,11 +99,15 @@ var gStr = {
 };
 
 // This lazily initializes the string bundle upon first use.
-this.__defineGetter__("gBundle", function() {
-  delete this.gBundle;
-  return this.gBundle = Cc["@mozilla.org/intl/stringbundle;1"].
-                        getService(Ci.nsIStringBundleService).
-                        createBundle(kDownloadProperties);
+Object.defineProperty(this, "gBundle", {
+  configurable: true,
+  enumerable: true,
+  get() {
+    delete this.gBundle;
+    return this.gBundle = Cc["@mozilla.org/intl/stringbundle;1"].
+                          getService(Ci.nsIStringBundleService).
+                          createBundle(kDownloadProperties);
+  },
 });
 
 // Keep track of at most this many second/lastSec pairs so that multiple calls