--- a/toolkit/components/extensions/ExtensionParent.jsm
+++ b/toolkit/components/extensions/ExtensionParent.jsm
@@ -1724,24 +1724,36 @@ class CacheStore {
     StartupCache.save();
   }
 }
 
 for (let name of StartupCache.STORE_NAMES) {
   StartupCache[name] = new CacheStore(name);
 }
 
+function makeStartupPromise(event) {
+  return ExtensionUtils.promiseObserved(event).then(() => {});
+}
+
+// browserPaintedPromise and browserStartupPromise are promises that
+// resolve after the first browser window is painted and after browser
+// windows have been restored, respectively.
+let browserPaintedPromise = makeStartupPromise("browser-delayed-startup-finished");
+let browserStartupPromise = makeStartupPromise("sessionstore-windows-restored");
+
 var ExtensionParent = {
   GlobalManager,
   HiddenExtensionPage,
   IconDetails,
   ParentAPIManager,
   StartupCache,
   WebExtensionPolicy,
   apiManager,
+  browserPaintedPromise,
+  browserStartupPromise,
   promiseExtensionViewLoaded,
   watchExtensionProxyContextLoad,
   DebugUtils,
 };
 
 XPCOMUtils.defineLazyGetter(ExtensionParent, "PlatformInfo", () => {
   return Object.freeze({
     os: (function() {

--- a/toolkit/components/extensions/parent/.eslintrc.js
+++ b/toolkit/components/extensions/parent/.eslintrc.js
@@ -9,18 +9,16 @@ module.exports = {
     "InputEventManager": true,
     "PRIVATE_STORE": true,
     "TabBase": true,
     "TabManagerBase": true,
     "TabTrackerBase": true,
     "WindowBase": true,
     "WindowManagerBase": true,
     "WindowTrackerBase": true,
-    "browserPaintedPromise": true,
-    "browserStartupPromise": true,
     "getContainerForCookieStoreId": true,
     "getCookieStoreIdForContainer": true,
     "getCookieStoreIdForTab": true,
     "isContainerCookieStoreId": true,
     "isDefaultCookieStoreId": true,
     "isPrivateCookieStoreId": true,
     "isValidCookieStoreId": true,
   },

--- a/toolkit/components/extensions/parent/ext-backgroundPage.js
+++ b/toolkit/components/extensions/parent/ext-backgroundPage.js
@@ -1,16 +1,18 @@
 "use strict";
 
 ChromeUtils.defineModuleGetter(this, "TelemetryStopwatch",
                                "resource://gre/modules/TelemetryStopwatch.jsm");
 
 ChromeUtils.import("resource://gre/modules/ExtensionParent.jsm");
 var {
   HiddenExtensionPage,
+  browserPaintedPromise,
+  browserStartupPromise,
   promiseExtensionViewLoaded,
 } = ExtensionParent;
 
 XPCOMUtils.defineLazyPreferenceGetter(this, "DELAYED_STARTUP",
                                       "extensions.webextensions.background-delayed-startup");
 
 // Responsible for the background_page section of the manifest.
 class BackgroundPage extends HiddenExtensionPage {

--- a/toolkit/components/extensions/parent/ext-toolkit.js
+++ b/toolkit/components/extensions/parent/ext-toolkit.js
@@ -69,18 +69,8 @@ global.getContainerForCookieStoreId = fu
   return null;
 };
 
 global.isValidCookieStoreId = function(storeId) {
   return isDefaultCookieStoreId(storeId) ||
          isPrivateCookieStoreId(storeId) ||
          isContainerCookieStoreId(storeId);
 };
-
-function makeStartupPromise(event) {
-  return ExtensionUtils.promiseObserved(event).then(() => {});
-}
-
-// browserPaintedPromise and browserStartupPromise are promises that
-// resolve after the first browser window is painted and after browser
-// windows have been restored, respectively.
-global.browserPaintedPromise = makeStartupPromise("browser-delayed-startup-finished");
-global.browserStartupPromise = makeStartupPromise("sessionstore-windows-restored");