Fix to svc sample enocoder for visual studio build.
Fix to svc sample enocoder for visual studio build.

Fix to sample encoder, for visual studio buid failure:
conversion from 'uint64_t' to 'int'.

Change-Id: I385ab8482e1ee97da9872437f8286d9071e38e0e

webmproject/libvpx,webmproject/libvpx,webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx