Reenable running samplerstress GM in pipe mode.
Reenable running samplerstress GM in pipe mode.

It was disabled because samplerstress did was not
registered for flattening. Now that it is, do not
skip it when running GM in pipe mode.
Review URL: https://codereview.appspot.com/6305057

git-svn-id: e8541e15acce502a64c929015570ad1648e548cd@4196 2bbb7eff-a529-9590-31e7-b0007b416f81

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