report max pixel error on failure, rather than the hex of the first mismatched pixel Review URL: https://codereview.appspot.com/6826080
report max pixel error on failure, rather than the hex of the first mismatched pixel
Review URL: https://codereview.appspot.com/6826080

git-svn-id: e8541e15acce502a64c929015570ad1648e548cd@6365 2bbb7eff-a529-9590-31e7-b0007b416f81

Cue/skia,Cue/skia,Cue/skia,Cue/skia