diff --git a/browser/components/sessionstore/src/DocShellCapabilities.jsm b/browser/components/sessionstore/src/DocShellCapabilities.jsm
new file mode 100644
index 00000000000..293a6bbcd1c
--- /dev/null
+++ b/browser/components/sessionstore/src/DocShellCapabilities.jsm
@@ -0,0 +1,50 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+* License, v. 2.0. If a copy of the MPL was not distributed with this file,
+* You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+this.EXPORTED_SYMBOLS = ["DocShellCapabilities"];
+
+/**
+ * The external API exported by this module.
+ */
+this.DocShellCapabilities = Object.freeze({
+  collect: function (docShell) {
+    return DocShellCapabilitiesInternal.collect(docShell);
+  },
+
+  restore: function (docShell, disallow) {
+    return DocShellCapabilitiesInternal.restore(docShell, disallow);
+  },
+});
+
+/**
+ * Internal functionality to save and restore the docShell.allow* properties.
+ */
+let DocShellCapabilitiesInternal = {
+  // List of docShell capabilities to (re)store. These are automatically
+  // retrieved from a given docShell if not already collected before.
+  // This is made so they're automatically in sync with all nsIDocShell.allow*
+  // properties.
+  caps: null,
+
+  allCapabilities: function (docShell) {
+    if (!this.caps) {
+      let keys = Object.keys(docShell);
+      this.caps = keys.filter(k => k.startsWith("allow")).map(k => k.slice(5));
+    }
+    return this.caps;
+  },
+
+  collect: function (docShell) {
+    let caps = this.allCapabilities(docShell);
+    return caps.filter(cap => !docShell["allow" + cap]);
+  },
+
+  restore: function (docShell, disallow) {
+    let caps = this.allCapabilities(docShell);
+    for (let cap of caps)
+      docShell["allow" + cap] = !disallow.has(cap);
+  },
+};
diff --git a/browser/components/sessionstore/src/SessionStore.jsm b/browser/components/sessionstore/src/SessionStore.jsm
index 5569fb80a83..388c251d12b 100644
--- a/browser/components/sessionstore/src/SessionStore.jsm
+++ b/browser/components/sessionstore/src/SessionStore.jsm
@@ -94,23 +94,6 @@ XPCOMUtils.defineLazyServiceGetter(this, "gSessionStartup",
 XPCOMUtils.defineLazyServiceGetter(this, "gScreenManager",
   "@mozilla.org/gfx/screenmanager;1", "nsIScreenManager");
 
-// List of docShell capabilities to (re)store. These are automatically
-// retrieved from a given docShell if not already collected before.
-// This is made so they're automatically in sync with all nsIDocShell.allow*
-// properties.
-let gDocShellCapabilities = (function () {
-  let caps;
-
-  return docShell => {
-    if (!caps) {
-      let keys = Object.keys(docShell);
-      caps = keys.filter(k => k.startsWith("allow")).map(k => k.slice(5));
-    }
-
-    return caps;
-  };
-})();
-
 /**
  * Get nsIURI from string
  * @param string
@@ -122,6 +105,8 @@ function makeURI(aString) {
 
 XPCOMUtils.defineLazyModuleGetter(this, "ScratchpadManager",
   "resource:///modules/devtools/scratchpad-manager.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "DocShellCapabilities",
+  "resource:///modules/sessionstore/DocShellCapabilities.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "DocumentUtils",
   "resource:///modules/sessionstore/DocumentUtils.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "Messenger",
@@ -2584,7 +2569,8 @@ let SessionStoreInternal = {
    */
   restoreHistory:
     function ssi_restoreHistory(aWindow, aTabs, aTabData, aIdMap, aDocIdentMap,
-                                aRestoreImmediately) {
+                                aRestoreImmediately)
+  {
     // if the tab got removed before being completely restored, then skip it
     while (aTabs.length > 0 && !(this._canRestoreTabHistory(aTabs[0]))) {
       aTabs.shift();
@@ -2631,8 +2617,7 @@ let SessionStoreInternal = {
 
     // make sure to reset the capabilities and attributes, in case this tab gets reused
     let disallow = new Set(tabData.disallow && tabData.disallow.split(","));
-    for (let cap of gDocShellCapabilities(browser.docShell))
-      browser.docShell["allow" + cap] = !disallow.has(cap);
+    DocShellCapabilities.restore(browser.docShell, disallow);
 
     // Restore tab attributes.
     if ("attributes" in tabData) {
@@ -4503,10 +4488,7 @@ let TabState = {
       delete tabData.pinned;
     tabData.hidden = tab.hidden;
 
-    let disallow = [];
-    for (let cap of gDocShellCapabilities(browser.docShell))
-      if (!browser.docShell["allow" + cap])
-        disallow.push(cap);
+    let disallow = DocShellCapabilities.collect(browser.docShell);
     if (disallow.length > 0)
       tabData.disallow = disallow.join(",");
     else if (tabData.disallow)
diff --git a/browser/components/sessionstore/src/moz.build b/browser/components/sessionstore/src/moz.build
index 4c5fe85ef08..39d9dd99e84 100644
--- a/browser/components/sessionstore/src/moz.build
+++ b/browser/components/sessionstore/src/moz.build
@@ -13,6 +13,7 @@ EXTRA_COMPONENTS += [
 JS_MODULES_PATH = 'modules/sessionstore'
 
 EXTRA_JS_MODULES = [
+    'DocShellCapabilities.jsm',
     'DocumentUtils.jsm',
     'Messenger.jsm',
     'PrivacyLevel.jsm',