Fix Visual Studio build warning
Fix Visual Studio build warning

Fixed warning C4244: '-=' : conversion from 'const double' to 'int',
possible loss of data.

Change-Id: Ic4691346037767b244e7f71248c2f871f92002f3

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