Promote to uint32_t before left shift
Promote to uint32_t before left shift

This commit change to promote uint8_t explicitly to uint32_t before
left shift operation.

BUG=https://bugs.chromium.org/p/chromium/issues/detail?id=612021

Change-Id: Id7059154efb5bdfa45889dabe72aaafd46d79f23

mbebenita/aom,mwgoldsmith/vpx,webmproject/libvpx,webmproject/libvpx,mbebenita/aom,GrokImageCompression/aom,GrokImageCompression/aom,mwgoldsmith/libvpx,webmproject/libvpx,mbebenita/aom,smarter/aom,ShiftMediaProject/libvpx,mbebenita/aom,mwgoldsmith/libvpx,Topopiccione/libvpx,webmproject/libvpx,GrokImageCompression/aom,mbebenita/aom,mbebenita/aom,luctrudeau/aom,mwgoldsmith/vpx,smarter/aom,smarter/aom,webmproject/libvpx,smarter/aom,mwgoldsmith/libvpx,mwgoldsmith/libvpx,ShiftMediaProject/libvpx,Topopiccione/libvpx,mwgoldsmith/vpx,luctrudeau/aom,mwgoldsmith/libvpx,luctrudeau/aom,mbebenita/aom,mwgoldsmith/vpx,mwgoldsmith/vpx,webmproject/libvpx,Topopiccione/libvpx,GrokImageCompression/aom,luctrudeau/aom,luctrudeau/aom,smarter/aom,luctrudeau/aom,mbebenita/aom,GrokImageCompression/aom,GrokImageCompression/aom,Topopiccione/libvpx,mwgoldsmith/vpx,Topopiccione/libvpx,ShiftMediaProject/libvpx,Topopiccione/libvpx,mbebenita/aom,smarter/aom,mwgoldsmith/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx