1 files changed, 68 insertions, 0 deletions
diff --git a/dom/localstorage/LSObserver.h b/dom/localstorage/LSObserver.h
new file mode 100644
index 0000000000..55107bc6c4
--- /dev/null
+++ b/dom/localstorage/LSObserver.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+
+#ifndef mozilla_dom_localstorage_LSObserver_h
+#define mozilla_dom_localstorage_LSObserver_h
+
+#include "mozilla/Assertions.h"
+#include "nsISupports.h"
+#include "nsString.h"
+
+namespace mozilla::dom {
+
+class LSObserverChild;
+
+/**
+ * Effectively just a refcounted life-cycle management wrapper around
+ * LSObserverChild which exists to receive "storage" event information from
+ * other processes.  (Same-process events are handled within the process, see
+ * `LSObject::OnChange`.)
+ *
+ * ## Lifecycle ##
+ * - Created by LSObject::EnsureObserver via synchronous LSRequest idiom
+ *   whenever the first window's origin adds a "storage" event.  Placed in the
+ *   gLSObservers LSObserverHashtable for subsequent LSObject's via
+ *   LSObserver::Get lookup.
+ * - The LSObserverChild directly handles "Observe" messages, shunting them
+ *   directly to Storage::NotifyChange which does all the legwork of notifying
+ *   windows about "storage" events.
+ * - Destroyed when refcount goes to zero due to all owning LSObjects being
+ *   destroyed or having their `LSObject::DropObserver` methods invoked due to
+ *   the last "storage" event listener being removed from the owning window.
+ */
+class LSObserver final {
+  friend class LSObject;
+
+  LSObserverChild* mActor;
+
+  const nsCString mOrigin;
+
+ public:
+  static LSObserver* Get(const nsACString& aOrigin);
+
+  NS_INLINE_DECL_REFCOUNTING(LSObserver)
+
+  void AssertIsOnOwningThread() const { NS_ASSERT_OWNINGTHREAD(LSObserver); }
+
+  void SetActor(LSObserverChild* aActor);
+
+  void ClearActor() {
+    AssertIsOnOwningThread();
+    MOZ_ASSERT(mActor);
+
+    mActor = nullptr;
+  }
+
+ private:
+  // Only created by LSObject.
+  explicit LSObserver(const nsACString& aOrigin);
+
+  ~LSObserver();
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_localstorage_LSObserver_h