Roll external/skia dd732d481..67cf6896f (1 commits)

https://skia.googlesource.com/skia.git/+log/dd732d481..67cf6896f

2017-10-11 angle-deps-roller@chromium.org Roll skia/third_party/externals/angle2/ bd159f067..78507c6ee (1 commit)

Test: Presubmit checks will test this change.
Change-Id: I5a72a86ba737883ec90282a62f818924b758770e
Exempt-From-Owner-Approval: The autoroll bot does not require owner approval.