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diff --git a/toolkit/components/extensions/storage/ExtensionStorageComponents.sys.mjs b/toolkit/components/extensions/storage/ExtensionStorageComponents.sys.mjs
new file mode 100644
index 0000000000..b02b0d53e8
--- /dev/null
+++ b/toolkit/components/extensions/storage/ExtensionStorageComponents.sys.mjs
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+/* 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 lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  AsyncShutdown: "resource://gre/modules/AsyncShutdown.sys.mjs",
+  FileUtils: "resource://gre/modules/FileUtils.sys.mjs",
+});
+
+const StorageSyncArea = Components.Constructor(
+  "@mozilla.org/extensions/storage/internal/sync-area;1",
+  "mozIConfigurableExtensionStorageArea",
+  "configure"
+);
+
+/**
+ * An XPCOM service for the WebExtension `storage.sync` API. The service manages
+ * a storage area for storing and syncing extension data.
+ *
+ * The service configures its storage area with the database path, and hands
+ * out references to the configured area via `getInterface`. It also registers
+ * a shutdown blocker to automatically tear down the area.
+ *
+ * ## What's the difference between `storage/internal/storage-sync-area;1` and
+ *    `storage/sync;1`?
+ *
+ * `components.conf` has two classes:
+ * `@mozilla.org/extensions/storage/internal/sync-area;1` and
+ * `@mozilla.org/extensions/storage/sync;1`.
+ *
+ * The `storage/internal/sync-area;1` class is implemented in Rust, and can be
+ * instantiated using `createInstance` and `Components.Constructor`. It's not
+ * a singleton, so creating a new instance will create a new `storage.sync`
+ * area, with its own database connection. It's useful for testing, but not
+ * meant to be used outside of this module.
+ *
+ * The `storage/sync;1` class is implemented in this file. It's a singleton,
+ * ensuring there's only one `storage.sync` area, with one database connection.
+ * The service implements `nsIInterfaceRequestor`, so callers can access the
+ * storage interface like this:
+ *
+ *     let storageSyncArea = Cc["@mozilla.org/extensions/storage/sync;1"]
+ *        .getService(Ci.nsIInterfaceRequestor)
+ *        .getInterface(Ci.mozIExtensionStorageArea);
+ *
+ * ...And the Sync interface like this:
+ *
+ *    let extensionStorageEngine = Cc["@mozilla.org/extensions/storage/sync;1"]
+ *       .getService(Ci.nsIInterfaceRequestor)
+ *       .getInterface(Ci.mozIBridgedSyncEngine);
+ *
+ * @class
+ */
+export function StorageSyncService() {
+  if (StorageSyncService._singleton) {
+    return StorageSyncService._singleton;
+  }
+
+  let file = lazy.FileUtils.getFile("ProfD", ["storage-sync-v2.sqlite"]);
+  let kintoFile = lazy.FileUtils.getFile("ProfD", ["storage-sync.sqlite"]);
+  this._storageArea = new StorageSyncArea(file, kintoFile);
+
+  // Register a blocker to close the storage connection on shutdown.
+  this._shutdownBound = () => this._shutdown();
+  lazy.AsyncShutdown.profileChangeTeardown.addBlocker(
+    "StorageSyncService: shutdown",
+    this._shutdownBound
+  );
+
+  StorageSyncService._singleton = this;
+}
+
+StorageSyncService._singleton = null;
+
+StorageSyncService.prototype = {
+  QueryInterface: ChromeUtils.generateQI(["nsIInterfaceRequestor"]),
+
+  // Returns the storage and syncing interfaces. This just hands out a
+  // reference to the underlying storage area, with a quick check to make sure
+  // that callers are asking for the right interfaces.
+  getInterface(iid) {
+    if (
+      iid.equals(Ci.mozIExtensionStorageArea) ||
+      iid.equals(Ci.mozIBridgedSyncEngine)
+    ) {
+      return this._storageArea.QueryInterface(iid);
+    }
+    throw Components.Exception(
+      "This interface isn't implemented",
+      Cr.NS_ERROR_NO_INTERFACE
+    );
+  },
+
+  // Tears down the storage area and lifts the blocker so that shutdown can
+  // continue.
+  async _shutdown() {
+    try {
+      await new Promise((resolve, reject) => {
+        this._storageArea.teardown({
+          handleSuccess: resolve,
+          handleError(code, message) {
+            reject(Components.Exception(message, code));
+          },
+        });
+      });
+    } finally {
+      lazy.AsyncShutdown.profileChangeTeardown.removeBlocker(
+        this._shutdownBound
+      );
+    }
+  },
+};