1 files changed, 4 insertions, 0 deletions
diff --git a/widget/windows/WinCompositorWidget.h b/widget/windows/WinCompositorWidget.h
index 9661cab45..1689a8641 100644
--- a/widget/windows/WinCompositorWidget.h
+++ b/widget/windows/WinCompositorWidget.h
@@ -10,6 +10,7 @@
 #include "gfxASurface.h"
 #include "mozilla/gfx/CriticalSection.h"
 #include "mozilla/gfx/Point.h"
+#include "mozilla/Mutex.h"
 #include "nsIWidget.h"
 
 class nsWindow;
@@ -83,6 +84,8 @@ public:
     return mWnd;
   }
 
+  mozilla::Mutex& GetTransparentSurfaceLock() { return mTransparentSurfaceLock; }
+
 private:
   HDC GetWindowSurface();
   void FreeWindowSurface(HDC dc);
@@ -95,6 +98,7 @@ private:
   gfx::CriticalSection mPresentLock;
 
   // Transparency handling.
+  mozilla::Mutex mTransparentSurfaceLock;
   nsTransparencyMode mTransparencyMode;
   RefPtr<gfxASurface> mTransparentSurface;
   HDC mMemoryDC;