Roll external/skia 5563d8da7..8296e752f (2 commits)

https://skia.googlesource.com/skia.git/+log/5563d8da7..8296e752f

2017-08-25 robertphillips@google.com Switch atlas clients over to using absolute texture coordinates (take 2)
2017-08-25 caryclark@skia.org tiny concave path point fix

Test: Presubmit checks will test this change.
Change-Id: I90076ff3119bfd432c9bf33514e143ee7c7e26d7