lossless: Remove about 25 % of the speed degradation
lossless: Remove about 25 % of the speed degradation

introduced in:
"lossless: 0.37 % compression density improvement"

Uses the statistics of red and blue histograms to decide if to run
cross color correction at all.

Improves compression density by 0.02 % or so.

Change-Id: I47429557e9cdbd9fa90c584696f241b17427d73f

PKRoma/libwebp,rxl194/libwebp,rxl194/libwebp,webmproject/libwebp,yohunl/libwebp,ya7lelkom/libwebp,ya7lelkom/libwebp,ttyangf/libwebp,webmproject/libwebp,zofuthan/libwebp,webmproject/libwebp,yohunl/libwebp,PKRoma/libwebp,zofuthan/libwebp,imazen/libwebp,zofuthan/libwebp,imazen/libwebp,Aexyn/libwebp,imazen/libwebp,ttyangf/libwebp,Aexyn/libwebp,rxl194/libwebp,Aexyn/libwebp,PKRoma/libwebp,PKRoma/libwebp,PKRoma/libwebp,ya7lelkom/libwebp,webmproject/libwebp,redengineer/libwebp,ttyangf/libwebp,Aexyn/libwebp,imazen/libwebp,zofuthan/libwebp,imazen/libwebp,ya7lelkom/libwebp,rxl194/libwebp,yohunl/libwebp,rxl194/libwebp,redengineer/libwebp,ttyangf/libwebp,zofuthan/libwebp,Aexyn/libwebp,ttyangf/libwebp,redengineer/libwebp,redengineer/libwebp,redengineer/libwebp,webmproject/libwebp,ya7lelkom/libwebp,yohunl/libwebp,yohunl/libwebp,PKRoma/libwebp