Refactor out zero motion vector equivalence.
Refactor out zero motion vector equivalence.

Change-Id: I6b20248b6f76545356f910ca6386f5466e287b6e

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