Speedup method StoreImageToBitMask by 5%.
Speedup method StoreImageToBitMask by 5%.

Speedup method StoreImageToBitMask by replacing the code to find histogram
index and Huffman tree codes at every iteration to a more optimal code that
updates these only when the current pixel (to write) crosses the histogram
tile-row boundary.

This change speeds up the StoreImageToBitMask method by 5%.

Change-Id: If01a1ccd7820f9a3a3e5bc449d070defa51be14b

abwiz0086/webm.libwebp,Acidburn0zzz/webm.libwebp,altogother/webm.libwebp,redengineer/libwebp,yohunl/libwebp,ericmckean/webm.libwebp,gshORTON/webm.libwebp,iniwf/webm.libwebp,matanbs/webm.libwebp,kim42083/webm.libwebp,ya7lelkom/libwebp,PKRoma/libwebp,webmproject/libwebp,kleopatra999/webm.libwebp,iniwf/webm.libwebp,zofuthan/libwebp,rxl194/libwebp,zofuthan/libwebp,ttyangf/libwebp,gshORTON/webm.libwebp,zofuthan/libwebp,altogother/webm.libwebp,webmproject/libwebp,ttyangf/libwebp,Aexyn/libwebp,Maria1099/webm.libwebp,matanbs/webm.libwebp,kalli123/webm.libwebp,rxl194/libwebp,imazen/libwebp,Acidburn0zzz/webm.libwebp,kalli123/webm.libwebp,yohunl/libwebp,jiehu5114/libwebp,imazen/libwebp,jiehu5114/libwebp,Acidburn0zzz/webm.libwebp,Aexyn/libwebp,rxl194/libwebp,kalli123/webm.libwebp,abwiz0086/webm.libwebp,imazen/libwebp,jiehu5114/libwebp,zofuthan/libwebp,reimaginemedia/webm.libwebp,altogother/webm.libwebp,kim42083/webm.libwebp,altogother/webm.libwebp,redengineer/libwebp,kalli123/webm.libwebp,Suvarna1488/webm.libwebp,rxl194/libwebp,redengineer/libwebp,kleopatra999/webm.libwebp,reimaginemedia/webm.libwebp,gshORTON/webm.libwebp,ericmckean/webm.libwebp,ya7lelkom/libwebp,kim42083/webm.libwebp,ericmckean/webm.libwebp,imazen/libwebp,Aexyn/libwebp,Acidburn0zzz/webm.libwebp,matanbs/webm.libwebp,iniwf/webm.libwebp,Aexyn/libwebp,jacklicn/libwebp,PKRoma/libwebp,reimaginemedia/webm.libwebp,ttyangf/libwebp,ericmckean/webm.libwebp,jacklicn/libwebp,PKRoma/libwebp,yohunl/libwebp,iniwf/webm.libwebp,gshORTON/webm.libwebp,iniwf/webm.libwebp,PKRoma/libwebp,ya7lelkom/libwebp,Suvarna1488/webm.libwebp,Maria1099/webm.libwebp,altogother/webm.libwebp,yohunl/libwebp,abwiz0086/webm.libwebp,Aexyn/libwebp,kleopatra999/webm.libwebp,ericmckean/webm.libwebp,PKRoma/libwebp,reimaginemedia/webm.libwebp,Maria1099/webm.libwebp,webmproject/libwebp,kim42083/webm.libwebp,kleopatra999/webm.libwebp,jacklicn/libwebp,yohunl/libwebp,Suvarna1488/webm.libwebp,ya7lelkom/libwebp,kalli123/webm.libwebp,abwiz0086/webm.libwebp,Suvarna1488/webm.libwebp,kim42083/webm.libwebp,abwiz0086/webm.libwebp,ya7lelkom/libwebp,Suvarna1488/webm.libwebp,rxl194/libwebp,matanbs/webm.libwebp,Maria1099/webm.libwebp,matanbs/webm.libwebp,redengineer/libwebp,jiehu5114/libwebp,webmproject/libwebp,reimaginemedia/webm.libwebp,jacklicn/libwebp,redengineer/libwebp,gshORTON/webm.libwebp,webmproject/libwebp,jacklicn/libwebp,ttyangf/libwebp,Acidburn0zzz/webm.libwebp,ttyangf/libwebp,PKRoma/libwebp,jiehu5114/libwebp,kleopatra999/webm.libwebp,Maria1099/webm.libwebp,imazen/libwebp,zofuthan/libwebp