optimize (un)premultiplyAlpha: only divide when we have to
optimize (un)premultiplyAlpha: only divide when we have to

mozilla/shumway,mbebenita/shumway,mozilla/shumway,yurydelendik/shumway,mozilla/shumway,mozilla/shumway,yurydelendik/shumway,yurydelendik/shumway,yurydelendik/shumway,mozilla/shumway,mbebenita/shumway,mozilla/shumway,tschneidereit/shumway,yurydelendik/shumway,mozilla/shumway,mbebenita/shumway,tschneidereit/shumway,tschneidereit/shumway,tschneidereit/shumway,mbebenita/shumway,mozilla/shumway,mbebenita/shumway,mbebenita/shumway,yurydelendik/shumway,tschneidereit/shumway,tschneidereit/shumway,mbebenita/shumway,yurydelendik/shumway,yurydelendik/shumway,tschneidereit/shumway,tschneidereit/shumway,mbebenita/shumway