Roll external/skia 91e0d7526944..b1ff79aae809 (3 commits)

https://skia.googlesource.com/skia.git/+log/91e0d7526944..b1ff79aae809

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://skia-autoroll.corp.goog/r/android-master-autoroll
Please CC nifong@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

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

Test: Presubmit checks will test this change.
Change-Id: I18417dbef04acd833546f836433051e740a6c5e4
Exempt-From-Owner-Approval: The autoroll bot does not require owner approval.