[GPU] Allow kMulRGBByAlpha_InConfigFlag and kSwapRAndB_InConfigFlag to both be set
[GPU] Allow kMulRGBByAlpha_InConfigFlag and kSwapRAndB_InConfigFlag to both be set

Review URL: http://codereview.appspot.com/5433049/



git-svn-id: e8541e15acce502a64c929015570ad1648e548cd@2733 2bbb7eff-a529-9590-31e7-b0007b416f81

mrobinson/skia,Cue/skia,mrobinson/skia,metajack/skia,metajack/skia,Cue/skia,metajack/skia,Cue/skia,mrobinson/skia,Cue/skia,mrobinson/skia,mrobinson/skia,metajack/skia