Created attachment 30415 [details] [review]
Patch as described

Currently the pitch used for the render-buffer created to wrap a texture is:

 texImage->Width * rrb->cpp;

But the pitch we need to use is the pitch from the miptree. And in fact, we want to use the pitch of the texture level we are rendering to.

The attached patch does this; I've only tested with rendering to level 0, and I think there might be another bug for rendering to levels other than 0 - it would seem that we need to set rrb->base.Width/Height to be the width/height of the level as well.

Patch is against 7.6 branch, but HEAD looks identical.