1 files changed, 44 insertions, 0 deletions
diff --git a/layout/base/nsRefreshObservers.cpp b/layout/base/nsRefreshObservers.cpp
new file mode 100644
index 0000000000..d5fbb67444
--- /dev/null
+++ b/layout/base/nsRefreshObservers.cpp
@@ -0,0 +1,44 @@
+/* -*- 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/. */
+
+#include "nsRefreshObservers.h"
+#include "nsPresContext.h"
+
+namespace mozilla {
+
+ManagedPostRefreshObserver::ManagedPostRefreshObserver(nsPresContext* aPc,
+                                                       Action&& aAction)
+    : mPresContext(aPc), mAction(std::move(aAction)) {}
+
+ManagedPostRefreshObserver::ManagedPostRefreshObserver(nsPresContext* aPc)
+    : mPresContext(aPc) {}
+
+ManagedPostRefreshObserver::~ManagedPostRefreshObserver() = default;
+
+void ManagedPostRefreshObserver::Cancel() {
+  // Caller holds a strong reference, so no need to reference stuff from here.
+  mAction(true);
+  mAction = nullptr;
+  mPresContext = nullptr;
+}
+
+void ManagedPostRefreshObserver::DidRefresh() {
+  RefPtr<ManagedPostRefreshObserver> thisObject = this;
+
+  Unregister unregister = mAction(false);
+  if (unregister == Unregister::Yes) {
+    if (RefPtr<nsPresContext> pc = std::move(mPresContext)) {
+      // In theory mAction could've ended up in `Cancel` being called. In which
+      // case we're already unregistered so no need to do anything.
+      mAction = nullptr;
+      pc->UnregisterManagedPostRefreshObserver(this);
+    } else {
+      MOZ_DIAGNOSTIC_ASSERT(!mAction);
+    }
+  }
+}
+
+}  // namespace mozilla