Roll external/skia ba7196c0c..6d3af6faa (1 commits)

https://skia.googlesource.com/skia.git/+log/ba7196c0c..6d3af6faa

2017-08-11 skia-deps-roller@chromium.org Roll skia/third_party/externals/angle2/ d23bcd8eb..c2157a09d (1 commit)

Test: Presubmit checks will test this change.
Change-Id: If5b2b85c78068ef2a2a7ff8d4fa88078c7c8b1e1