Most of the validation errors are fixed from https://github.com/szeged/webrender/issues/80#issuecomment-488642315 (both Vulkan and DX12) There is two more left, which are related to the window resizing, but we can take care of those later since those only show up for one frame after the resize, hence we can threat them as low priority issues.
The first commit fixes the first error in https://github.com/szeged/webrender/issues/80#issuecomment-488642315, the second one fixes the second error and the errors related to the document example.
The WIP is there because I still need to figure out the dx12 debug layer errors and these changes are not tested on macOs yet.