Cleaning up sum_intra_stats function.
Cleaning up sum_intra_stats function.

Using size_group_lookup table and better variable names.

Change-Id: I6e67f2ce091845db43ace7d21b7ae31c6f165aec

abwiz0086/webm.libvpx,GrokImageCompression/aom,abwiz0086/webm.libvpx,altogother/webm.libvpx,Laknot/libvpx,smarter/aom,turbulenz/libvpx,liqianggao/libvpx,WebRTC-Labs/libvpx,webmproject/libvpx,Maria1099/webm.libvpx,matanbs/vp982,iniwf/webm.libvpx,ShiftMediaProject/libvpx,thdav/aom,Suvarna1488/webm.libvpx,kim42083/webm.libvpx,iniwf/webm.libvpx,kalli123/webm.libvpx,ittiamvpx/libvpx-1,kim42083/webm.libvpx,cinema6/libvpx,matanbs/vp982,shyamalschandra/libvpx,pcwalton/libvpx,cinema6/libvpx,reimaginemedia/webm.libvpx,sanyaade-teachings/libvpx,ittiamvpx/libvpx,shacklettbp/aom,goodleixiao/vpx,mwgoldsmith/vpx,felipebetancur/libvpx,kalli123/webm.libvpx,matanbs/vp982,smarter/aom,Maria1099/webm.libvpx,charup/https---github.com-webmproject-libvpx-,openpeer/libvpx_new,kim42083/webm.libvpx,turbulenz/libvpx,mwgoldsmith/vpx,ittiamvpx/libvpx-1,WebRTC-Labs/libvpx,reimaginemedia/webm.libvpx,gshORTON/webm.libvpx,Topopiccione/libvpx,felipebetancur/libvpx,turbulenz/libvpx,Topopiccione/libvpx,GrokImageCompression/aom,Laknot/libvpx,liqianggao/libvpx,GrokImageCompression/aom,ittiamvpx/libvpx-1,smarter/aom,jacklicn/webm.libvpx,webmproject/libvpx,pcwalton/libvpx,pcwalton/libvpx,jmvalin/aom,matanbs/vp982,mbebenita/aom,gshORTON/webm.libvpx,turbulenz/libvpx,mwgoldsmith/libvpx,shyamalschandra/libvpx,VTCSecureLLC/libvpx,luctrudeau/aom,zofuthan/libvpx,luctrudeau/aom,kalli123/webm.libvpx,running770/libvpx,mbebenita/aom,kalli123/webm.libvpx,stewnorriss/libvpx,shacklettbp/aom,jdm/libvpx,abwiz0086/webm.libvpx,Maria1099/webm.libvpx,abwiz0086/webm.libvpx,felipebetancur/libvpx,VTCSecureLLC/libvpx,felipebetancur/libvpx,charup/https---github.com-webmproject-libvpx-,altogother/webm.libvpx,iniwf/webm.libvpx,mbebenita/aom,luctrudeau/aom,matanbs/vp982,zofuthan/libvpx,Acidburn0zzz/webm.libvpx,GrokImageCompression/aom,jdm/libvpx,reimaginemedia/webm.libvpx,turbulenz/libvpx,liqianggao/libvpx,hsueceumd/test_hui,WebRTC-Labs/libvpx,shareefalis/libvpx,thdav/aom,mwgoldsmith/vpx,Distrotech/libvpx,thdav/aom,pcwalton/libvpx,liqianggao/libvpx,ittiamvpx/libvpx,zofuthan/libvpx,jdm/libvpx,matanbs/vp982,sanyaade-teachings/libvpx,shareefalis/libvpx,Acidburn0zzz/webm.libvpx,Distrotech/libvpx,openpeer/libvpx_new,Maria1099/webm.libvpx,turbulenz/libvpx,shareefalis/libvpx,n4t/libvpx,reimaginemedia/webm.libvpx,Maria1099/webm.libvpx,smarter/aom,hsueceumd/test_hui,stewnorriss/libvpx,n4t/libvpx,felipebetancur/libvpx,cinema6/libvpx,matanbs/webm.libvpx,iniwf/webm.libvpx,shareefalis/libvpx,luctrudeau/aom,kim42083/webm.libvpx,thdav/aom,hsueceumd/test_hui,webmproject/libvpx,ittiamvpx/libvpx,mbebenita/aom,goodleixiao/vpx,VTCSecureLLC/libvpx,mbebenita/aom,GrokImageCompression/aom,n4t/libvpx,charup/https---github.com-webmproject-libvpx-,ShiftMediaProject/libvpx,cinema6/libvpx,pcwalton/libvpx,Laknot/libvpx,running770/libvpx,altogother/webm.libvpx,hsueceumd/test_hui,cinema6/libvpx,matanbs/vp982,GrokImageCompression/aom,running770/libvpx,kleopatra999/webm.libvpx,Acidburn0zzz/webm.libvpx,charup/https---github.com-webmproject-libvpx-,kalli123/webm.libvpx,zofuthan/libvpx,kleopatra999/webm.libvpx,luctrudeau/aom,Distrotech/libvpx,gshORTON/webm.libvpx,lyx2014/libvpx_c,Suvarna1488/webm.libvpx,VTCSecureLLC/libvpx,jacklicn/webm.libvpx,jacklicn/webm.libvpx,webmproject/libvpx,jmvalin/aom,Laknot/libvpx,Distrotech/libvpx,abwiz0086/webm.libvpx,Topopiccione/libvpx,ittiamvpx/libvpx,openpeer/libvpx_new,mbebenita/aom,Suvarna1488/webm.libvpx,Acidburn0zzz/webm.libvpx,shacklettbp/aom,jmvalin/aom,jacklicn/webm.libvpx,openpeer/libvpx_new,lyx2014/libvpx_c,mwgoldsmith/libvpx,WebRTC-Labs/libvpx,reimaginemedia/webm.libvpx,webmproject/libvpx,lyx2014/libvpx_c,altogother/webm.libvpx,jmvalin/aom,kalli123/webm.libvpx,ittiamvpx/libvpx,felipebetancur/libvpx,iniwf/webm.libvpx,stewnorriss/libvpx,jacklicn/webm.libvpx,WebRTC-Labs/libvpx,liqianggao/libvpx,ittiamvpx/libvpx-1,Laknot/libvpx,ShiftMediaProject/libvpx,Suvarna1488/webm.libvpx,ShiftMediaProject/libvpx,goodleixiao/vpx,mwgoldsmith/libvpx,ittiamvpx/libvpx,sanyaade-teachings/libvpx,ShiftMediaProject/libvpx,gshORTON/webm.libvpx,openpeer/libvpx_new,shareefalis/libvpx,Distrotech/libvpx,jdm/libvpx,kleopatra999/webm.libvpx,reimaginemedia/webm.libvpx,mwgoldsmith/vpx,lyx2014/libvpx_c,jmvalin/aom,mwgoldsmith/libvpx,luctrudeau/aom,smarter/aom,Laknot/libvpx,Topopiccione/libvpx,gshORTON/webm.libvpx,kim42083/webm.libvpx,stewnorriss/libvpx,gshORTON/webm.libvpx,kleopatra999/webm.libvpx,n4t/libvpx,mbebenita/aom,goodleixiao/vpx,sanyaade-teachings/libvpx,sanyaade-teachings/libvpx,hsueceumd/test_hui,mwgoldsmith/libvpx,kim42083/webm.libvpx,Distrotech/libvpx,shyamalschandra/libvpx,shacklettbp/aom,mwgoldsmith/libvpx,Topopiccione/libvpx,openpeer/libvpx_new,shyamalschandra/libvpx,lyx2014/libvpx_c,Acidburn0zzz/webm.libvpx,matanbs/webm.libvpx,stewnorriss/libvpx,matanbs/webm.libvpx,zofuthan/libvpx,charup/https---github.com-webmproject-libvpx-,Maria1099/webm.libvpx,liqianggao/libvpx,pcwalton/libvpx,Suvarna1488/webm.libvpx,hsueceumd/test_hui,Topopiccione/libvpx,Acidburn0zzz/webm.libvpx,charup/https---github.com-webmproject-libvpx-,shyamalschandra/libvpx,lyx2014/libvpx_c,ittiamvpx/libvpx-1,smarter/aom,kleopatra999/webm.libvpx,thdav/aom,turbulenz/libvpx,n4t/libvpx,cinema6/libvpx,cinema6/libvpx,running770/libvpx,shareefalis/libvpx,jmvalin/aom,matanbs/webm.libvpx,turbulenz/libvpx,running770/libvpx,VTCSecureLLC/libvpx,jdm/libvpx,turbulenz/libvpx,matanbs/webm.libvpx,kleopatra999/webm.libvpx,zofuthan/libvpx,mwgoldsmith/vpx,mwgoldsmith/vpx,altogother/webm.libvpx,jdm/libvpx,VTCSecureLLC/libvpx,webmproject/libvpx,matanbs/webm.libvpx,jacklicn/webm.libvpx,iniwf/webm.libvpx,shyamalschandra/libvpx,Suvarna1488/webm.libvpx,ittiamvpx/libvpx-1,goodleixiao/vpx,stewnorriss/libvpx,altogother/webm.libvpx,shacklettbp/aom,mbebenita/aom,mbebenita/aom,running770/libvpx,thdav/aom,abwiz0086/webm.libvpx,goodleixiao/vpx,shacklettbp/aom