Short circuit rate_block in block_rd_txfm.
Short circuit rate_block in block_rd_txfm.

Don't run rate_block (cost_coeffs) if distortion alone is enough to
surpass best_rd.

This decreases 2nd pass runtime on HD at speed 2 by about 2%. There is
zero effect on output if tx_cache is removed.

Change-Id: Ia3b1cc77bfbe6ee988c395fde06c0eb92940b784

felipebetancur/libvpx,ittiamvpx/libvpx-1,smarter/aom,ShiftMediaProject/libvpx,jmvalin/aom,shacklettbp/aom,liqianggao/libvpx,smarter/aom,thdav/aom,thdav/aom,smarter/aom,openpeer/libvpx_new,Topopiccione/libvpx,felipebetancur/libvpx,ittiamvpx/libvpx-1,luctrudeau/aom,running770/libvpx,zofuthan/libvpx,shacklettbp/aom,shyamalschandra/libvpx,VTCSecureLLC/libvpx,GrokImageCompression/aom,shyamalschandra/libvpx,openpeer/libvpx_new,mbebenita/aom,mwgoldsmith/libvpx,running770/libvpx,webmproject/libvpx,shyamalschandra/libvpx,VTCSecureLLC/libvpx,mbebenita/aom,mwgoldsmith/libvpx,VTCSecureLLC/libvpx,jmvalin/aom,felipebetancur/libvpx,ittiamvpx/libvpx-1,zofuthan/libvpx,mwgoldsmith/vpx,shacklettbp/aom,zofuthan/libvpx,liqianggao/libvpx,Topopiccione/libvpx,mwgoldsmith/vpx,jmvalin/aom,shacklettbp/aom,mwgoldsmith/vpx,mwgoldsmith/libvpx,VTCSecureLLC/libvpx,felipebetancur/libvpx,mbebenita/aom,mbebenita/aom,webmproject/libvpx,jmvalin/aom,thdav/aom,VTCSecureLLC/libvpx,ShiftMediaProject/libvpx,mbebenita/aom,smarter/aom,GrokImageCompression/aom,openpeer/libvpx_new,shacklettbp/aom,mwgoldsmith/libvpx,shyamalschandra/libvpx,openpeer/libvpx_new,mwgoldsmith/libvpx,smarter/aom,jmvalin/aom,openpeer/libvpx_new,shyamalschandra/libvpx,jmvalin/aom,shacklettbp/aom,thdav/aom,mwgoldsmith/vpx,ShiftMediaProject/libvpx,running770/libvpx,felipebetancur/libvpx,running770/libvpx,mwgoldsmith/vpx,GrokImageCompression/aom,shyamalschandra/libvpx,Topopiccione/libvpx,ShiftMediaProject/libvpx,zofuthan/libvpx,mbebenita/aom,GrokImageCompression/aom,webmproject/libvpx,ittiamvpx/libvpx-1,GrokImageCompression/aom,Topopiccione/libvpx,thdav/aom,webmproject/libvpx,GrokImageCompression/aom,ShiftMediaProject/libvpx,liqianggao/libvpx,mbebenita/aom,luctrudeau/aom,VTCSecureLLC/libvpx,webmproject/libvpx,running770/libvpx,luctrudeau/aom,felipebetancur/libvpx,liqianggao/libvpx,liqianggao/libvpx,zofuthan/libvpx,luctrudeau/aom,Topopiccione/libvpx,mwgoldsmith/libvpx,luctrudeau/aom,smarter/aom,thdav/aom,ittiamvpx/libvpx-1,zofuthan/libvpx,liqianggao/libvpx,luctrudeau/aom,openpeer/libvpx_new,running770/libvpx,mbebenita/aom,webmproject/libvpx,Topopiccione/libvpx,mwgoldsmith/vpx,ittiamvpx/libvpx-1,mbebenita/aom