1 files changed, 29 insertions, 0 deletions
diff --git a/toolkit/modules/sessionstore/Utils.sys.mjs b/toolkit/modules/sessionstore/Utils.sys.mjs
new file mode 100644
index 0000000000..627cd22686
--- /dev/null
+++ b/toolkit/modules/sessionstore/Utils.sys.mjs
@@ -0,0 +1,29 @@
+/* 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/. */
+
+export var Utils = Object.freeze({
+  /**
+   * Restores frame tree |data|, starting at the given root |frame|. As the
+   * function recurses into descendant frames it will call cb(frame, data) for
+   * each frame it encounters, starting with the given root.
+   */
+  restoreFrameTreeData(frame, data, cb) {
+    // Restore data for the root frame.
+    // The callback can abort by returning false.
+    if (cb(frame, data) === false) {
+      return;
+    }
+
+    if (!data.hasOwnProperty("children")) {
+      return;
+    }
+
+    // Recurse into child frames.
+    SessionStoreUtils.forEachNonDynamicChildFrame(frame, (subframe, index) => {
+      if (data.children[index]) {
+        this.restoreFrameTreeData(subframe, data.children[index], cb);
+      }
+    });
+  },
+});