1 files changed, 46 insertions, 0 deletions
diff --git a/layout/base/nsRefreshObservers.cpp b/layout/base/nsRefreshObservers.cpp
new file mode 100644
index 0000000000..fe1635046c
--- /dev/null
+++ b/layout/base/nsRefreshObservers.cpp
@@ -0,0 +1,46 @@
+/* -*- 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 "PresShell.h"
+
+namespace mozilla {
+
+OneShotPostRefreshObserver::OneShotPostRefreshObserver(PresShell* aPresShell,
+                                                       Action&& aAction)
+    : mPresShell(aPresShell), mAction(std::move(aAction)) {}
+
+OneShotPostRefreshObserver::OneShotPostRefreshObserver(PresShell* aPresShell)
+    : mPresShell(aPresShell) {}
+
+OneShotPostRefreshObserver::~OneShotPostRefreshObserver() = default;
+
+void OneShotPostRefreshObserver::DidRefresh() {
+  if (!mPresShell) {
+    MOZ_ASSERT_UNREACHABLE(
+        "Post-refresh observer fired again after failed attempt at "
+        "unregistering it");
+    return;
+  }
+
+  RefPtr<OneShotPostRefreshObserver> kungfuDeathGrip = this;
+
+  mAction(mPresShell, this);
+
+  nsPresContext* presContext = mPresShell->GetPresContext();
+  if (!presContext) {
+    MOZ_ASSERT_UNREACHABLE(
+        "Unable to unregister post-refresh observer! Leaking it instead of "
+        "leaving garbage registered");
+    // Graceful handling, just in case...
+    mPresShell = nullptr;
+    mAction = Action();
+    return;
+  }
+  presContext->UnregisterOneShotPostRefreshObserver(this);
+}
+
+}  // namespace mozilla