1 files changed, 50 insertions, 0 deletions
diff --git a/widget/nsAutoRollup.cpp b/widget/nsAutoRollup.cpp
new file mode 100644
index 0000000000..9a043576df
--- /dev/null
+++ b/widget/nsAutoRollup.cpp
@@ -0,0 +1,50 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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 "mozilla/widget/nsAutoRollup.h"
+
+namespace mozilla {
+namespace widget {
+
+/*static*/
+uint32_t nsAutoRollup::sCount = 0;
+/*static*/
+StaticRefPtr<nsIContent> nsAutoRollup::sLastRollup;
+
+nsAutoRollup::nsAutoRollup() {
+  // remember if sLastRollup was null, and only clear it upon destruction
+  // if so. This prevents recursive usage of nsAutoRollup from clearing
+  // sLastRollup when it shouldn't.
+  mWasClear = !sLastRollup;
+  sCount++;
+}
+
+nsAutoRollup::nsAutoRollup(nsIContent* aRollup) {
+  MOZ_ASSERT(!sLastRollup);
+  mWasClear = true;
+  sCount++;
+  SetLastRollup(aRollup);
+}
+
+nsAutoRollup::~nsAutoRollup() {
+  if (sLastRollup && mWasClear) {
+    sLastRollup = nullptr;
+  }
+  sCount--;
+}
+
+/*static*/
+void nsAutoRollup::SetLastRollup(nsIContent* aLastRollup) {
+  // There must be at least one nsAutoRollup on the stack.
+  MOZ_ASSERT(sCount);
+
+  sLastRollup = aLastRollup;
+}
+
+/*static*/
+nsIContent* nsAutoRollup::GetLastRollup() { return sLastRollup.get(); }
+
+}  // namespace widget
+}  // namespace mozilla