So Moz2D source clipping seems to be working pretty well now (we started using it in bug 1044702). It looks like it's time to start using it in ClippedImage. We *do* lose caching of the clipped version of the image by making this change. That should be a win on all backends where Moz2D source clipping is copy-free, which is apparently everywhere but D2D 1.0. Users on Windows Vista and some versions of Windows 7 *do* use D2D 1.0, unfortunately, so this may be a regression for them in the short term. However, I understand that we're planning on dropping that backend and switching those users over to the GDI backend, which implements Moz2D source clipping without copying, so this should be a temporary pain. In exchange, we get performance improvements everywhere else, since caching has a cost and by not needing to cache anymore we will end up making things faster!