diff -r 000000000000 -r 6474c204b198 gfx/thebes/gfxReusableImageSurfaceWrapper.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gfx/thebes/gfxReusableImageSurfaceWrapper.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,61 @@
+/* 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 "gfxReusableImageSurfaceWrapper.h"
+#include "gfxImageSurface.h"
+
+gfxReusableImageSurfaceWrapper::gfxReusableImageSurfaceWrapper(gfxImageSurface* aSurface)
+  : mSurface(aSurface)
+{
+  MOZ_COUNT_CTOR(gfxReusableImageSurfaceWrapper);
+}
+
+gfxReusableImageSurfaceWrapper::~gfxReusableImageSurfaceWrapper()
+{
+  MOZ_COUNT_DTOR(gfxReusableImageSurfaceWrapper);
+}
+
+void
+gfxReusableImageSurfaceWrapper::ReadLock()
+{
+  NS_ASSERT_OWNINGTHREAD(gfxReusableImageSurfaceWrapper);
+  AddRef();
+}
+
+void
+gfxReusableImageSurfaceWrapper::ReadUnlock()
+{
+  Release();
+}
+
+gfxReusableSurfaceWrapper*
+gfxReusableImageSurfaceWrapper::GetWritable(gfxImageSurface** aSurface)
+{
+  NS_ASSERT_OWNINGTHREAD(gfxReusableImageSurfaceWrapper);
+
+  if (mRefCnt == 1) {
+    *aSurface = mSurface;
+    return this;
+  }
+
+  // Something else is reading the surface, copy it
+  gfxImageSurface* copySurface = new gfxImageSurface(mSurface->GetSize(), mSurface->Format(), false);
+  copySurface->CopyFrom(mSurface);
+  *aSurface = copySurface;
+
+  return new gfxReusableImageSurfaceWrapper(copySurface);
+}
+
+const unsigned char*
+gfxReusableImageSurfaceWrapper::GetReadOnlyData() const
+{
+  return mSurface->Data();
+}
+
+gfxImageFormat
+gfxReusableImageSurfaceWrapper::Format()
+{
+  return mSurface->Format();
+}
+