Roll external/skia 968af43f7..11f898f15 (2 commits)

https://skia.googlesource.com/skia.git/+log/968af43f7..11f898f15

2017-07-18 update-skps@skia.org Update SKP version
2017-07-18 csmartdalton@google.com gl: print shader sources one line at a time

Test: Presubmit checks will test this change.
Change-Id: I4a595876932e8fa73fea99e0270959e5cb16489d