Roll external/skia 6d3af6faa..32fa51041 (1 commits)

https://skia.googlesource.com/skia.git/+log/6d3af6faa..32fa51041

2017-08-11 benjaminwagner@google.com Abort dm/nanobench on bad configs.

Test: Presubmit checks will test this change.
Change-Id: Iace2619dbc9a866c0b48134c873fb67b3b7d9a3f