Roll external/skia 1ba5bfe59..3cc809294 (1 commits)

https://skia.googlesource.com/skia.git/+log/1ba5bfe59..3cc809294

2017-11-29 angle-deps-roller@chromium.org Roll skia/third_party/externals/angle2/ 57ea533f7..f13cadd8b (1 commit)

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Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, please contact the current sheriff, who should
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Test: Presubmit checks will test this change.
Change-Id: I95066b83226978e38cdcc8925e184c8f8691662c
Exempt-From-Owner-Approval: The autoroll bot does not require owner approval.