bc341912b1
bug:17600162 Transparent draws are not safe to reject for all xfermodes other than clear. Now, to be safe, only perform the rejection for SrcOver draws since other modes are fairly uncommon. We could specifically determine whether the xfermode could change the output given a transparent input, but there's little to be gained from the additional complexity. Change-Id: Ia699ac4bdc4da3353955840b53f1922d3cb1d85d