demux: strictly enforce the animation flag
demux: strictly enforce the animation flag

if the flag is incorrectly set in a VP8L or VP8/ALPH single image file
the demux will now fail.

Change-Id: Id4d5f2d3f6922a29b442c5d3d0acbe3d679e468a

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