diff -r 000000000000 -r 6474c204b198 widget/WidgetUtils.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/widget/WidgetUtils.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,31 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: sw=2 ts=8 et :
+ */
+/* 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_WidgetUtils_h
+#define mozilla_WidgetUtils_h
+
+#include "nsRect.h"
+#include "mozilla/gfx/Matrix.h"
+
+namespace mozilla {
+
+// NB: these must match up with pseudo-enum in nsIScreen.idl.
+enum ScreenRotation {
+  ROTATION_0 = 0,
+  ROTATION_90,
+  ROTATION_180,
+  ROTATION_270,
+
+  ROTATION_COUNT
+};
+
+gfx::Matrix ComputeTransformForRotation(const nsIntRect& aBounds,
+                                        ScreenRotation aRotation);
+
+} // namespace mozilla
+
+#endif // mozilla_WidgetUtils_h