D3D doesn't allow bigger viewports than rendertargets. But flipper does, so the viewport will be clipped and the transformation matrix will be changed.
This was done in the D3D backend itself. This is now moved into VideoCommon. This don't reduce code, but in this way, VideoCommon doesn't depend on the backends.
The upload in the backend isn't done, it's just pushed by the mostly removed SetMulti*SConstant4fv.
Also no optimizations was done on VideoCommon side, but I can start now :-)
Sorry for the hacky way, but I think this is a nice (working) snapshot for a much bigger change.