Regression fix for alpha channels using color cache:
Regression fix for alpha channels using color cache:

Considering the fact that insert to/lookup from the color cache is always 32
bit, use DecodeImageData() variant in that case.

Change-Id: I6c665a6cfbd9bd10651c1e82fa54e687cbd54a2b

Suvarna1488/webm.libwebp,PKRoma/libwebp,Suvarna1488/webm.libwebp,Aexyn/libwebp,Suvarna1488/webm.libwebp,gshORTON/webm.libwebp,PKRoma/libwebp,redengineer/libwebp,rxl194/libwebp,Tekserve/libwebp,kalli123/webm.libwebp,abwiz0086/webm.libwebp,webmproject/libwebp,rxl194/libwebp,appunite/libwebp,redengineer/libwebp,PKRoma/libwebp,appunite/libwebp,keane83/BLE_IM,jiehu5114/libwebp,comoyo/gonzo-libwebp,zofuthan/libwebp,rxl194/libwebp,kalli123/webm.libwebp,keane83/BLE_IM,Suvarna1488/webm.libwebp,comoyo/gonzo-libwebp,redengineer/libwebp,abwiz0086/webm.libwebp,altogother/webm.libwebp,PKRoma/libwebp,Tekserve/libwebp,rxl194/libwebp,kleopatra999/webm.libwebp,kim42083/webm.libwebp,jacklicn/libwebp,gshORTON/webm.libwebp,Aexyn/libwebp,PKRoma/libwebp,Tekserve/libwebp,imazen/libwebp,comoyo/gonzo-libwebp,jacklicn/libwebp,iniwf/webm.libwebp,kalli123/webm.libwebp,jiehu5114/libwebp,reimaginemedia/webm.libwebp,comoyo/gonzo-libwebp,ya7lelkom/libwebp,Aexyn/libwebp,ttyangf/libwebp,altogother/webm.libwebp,webmproject/libwebp,zofuthan/libwebp,keane83/BLE_IM,ya7lelkom/libwebp,kleopatra999/webm.libwebp,Aexyn/libwebp,kleopatra999/webm.libwebp,redengineer/libwebp,zofuthan/libwebp,Aexyn/libwebp,Acidburn0zzz/webm.libwebp,imazen/libwebp,iniwf/webm.libwebp,abwiz0086/webm.libwebp,matanbs/webm.libwebp,abwiz0086/webm.libwebp,kalli123/webm.libwebp,yohunl/libwebp,Acidburn0zzz/webm.libwebp,jacklicn/libwebp,webmproject/libwebp,altogother/webm.libwebp,appunite/libwebp,reimaginemedia/webm.libwebp,altogother/webm.libwebp,Maria1099/webm.libwebp,Maria1099/webm.libwebp,Maria1099/webm.libwebp,Tekserve/libwebp,jiehu5114/libwebp,reimaginemedia/webm.libwebp,appunite/libwebp,ericmckean/webm.libwebp,ya7lelkom/libwebp,ttyangf/libwebp,kim42083/webm.libwebp,iniwf/webm.libwebp,comoyo/gonzo-libwebp,ericmckean/webm.libwebp,yohunl/libwebp,imazen/libwebp,Acidburn0zzz/webm.libwebp,yohunl/libwebp,ya7lelkom/libwebp,Suvarna1488/webm.libwebp,reimaginemedia/webm.libwebp,imazen/libwebp,Maria1099/webm.libwebp,appunite/libwebp,altogother/webm.libwebp,keane83/BLE_IM,matanbs/webm.libwebp,comoyo/gonzo-libwebp,kim42083/webm.libwebp,reimaginemedia/webm.libwebp,jacklicn/libwebp,ya7lelkom/libwebp,iniwf/webm.libwebp,kim42083/webm.libwebp,PKRoma/libwebp,kleopatra999/webm.libwebp,gshORTON/webm.libwebp,gshORTON/webm.libwebp,keane83/BLE_IM,yohunl/libwebp,appunite/libwebp,ttyangf/libwebp,matanbs/webm.libwebp,kalli123/webm.libwebp,webmproject/libwebp,imazen/libwebp,yohunl/libwebp,ericmckean/webm.libwebp,gshORTON/webm.libwebp,ericmckean/webm.libwebp,Acidburn0zzz/webm.libwebp,zofuthan/libwebp,ttyangf/libwebp,Acidburn0zzz/webm.libwebp,redengineer/libwebp,ericmckean/webm.libwebp,rxl194/libwebp,matanbs/webm.libwebp,webmproject/libwebp,kleopatra999/webm.libwebp,iniwf/webm.libwebp,Maria1099/webm.libwebp,comoyo/gonzo-libwebp,jacklicn/libwebp,abwiz0086/webm.libwebp,kim42083/webm.libwebp,matanbs/webm.libwebp,zofuthan/libwebp,jiehu5114/libwebp,ttyangf/libwebp,jiehu5114/libwebp