[devopvoid]

• VideoBufferConverter passes direct buffers as slices and heap buffers with their array offset, position and remaining length, so slices and buffers with a position no longer read or write outside their window, and the size check applies to the window.
• The native byte array paths take an offset and a length, check them against the array, and hand the window's length to ConvertToI420.
• The position and limit of a buffer stay as they are; the unreachable destination path without an array is gone.