1 files changed, 31 insertions, 0 deletions
diff --git a/layout/painting/PaintTracker.h b/layout/painting/PaintTracker.h
new file mode 100644
index 0000000000..1f5554f983
--- /dev/null
+++ b/layout/painting/PaintTracker.h
@@ -0,0 +1,31 @@
+/* -*- 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_PaintTracker_h
+#define mozilla_PaintTracker_h
+
+#include "mozilla/Attributes.h"
+#include "nsDebug.h"
+
+namespace mozilla {
+
+class MOZ_STACK_CLASS PaintTracker {
+ public:
+  PaintTracker() { ++gPaintTracker; }
+  ~PaintTracker() {
+    NS_ASSERTION(gPaintTracker > 0, "Mismatched constructor/destructor");
+    --gPaintTracker;
+  }
+
+  static bool IsPainting() { return !!gPaintTracker; }
+
+ private:
+  static int gPaintTracker;
+};
+
+}  // namespace mozilla
+
+#endif  // mozilla_PaintTracker_h