feat: Start on new session restore, b=no-bug, c=no-component

src/zen/sessionstore/ZenSessionFile.sys.mjs

@@ -0,0 +1,27 @@
+// 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/.
+
+const FILE_NAME = 'zen-sessions.jsonlz4';
+
+export class nsZenSessionFile {
+  #path;
+
+  #windows;
+
+  constructor() {
+    this.#path = PathUtils.join(profileDir, FILE_NAME);
+  }
+
+  async read() {
+    try {
+      return await IOUtils.readJSON(this.#path, { compress: true });
+    } catch (e) {
+      return {};
+    }
+  }
+
+  async write(data) {
+    await IOUtils.writeJSON(this.#path, data, { compress: true });
+  }
+}