Roll external/skia 005fdd4ec..1a5e3e8c2 (8 commits)

https://skia.googlesource.com/skia.git/+log/005fdd4ec..1a5e3e8c2

2018-11-15 halcanary@google.com DEPS: update Harfbuzz to 2.1.1
2018-11-15 reed@google.com guard flag
2018-11-15 reed@google.com add flag to guard font apis
2018-11-15 halcanary@google.com SkPDF: pull out SkPDFSubsetFont code to another file.
2018-11-15 caryclark@skia.org fix pathops fuzz
2018-11-15 benjaminwagner@google.com Upgrade NVIDIA driver on Win10 QuadroP400 bots.
2018-11-15 reed@google.com create shared helper for strikecache and SkFont
2018-11-15 mtklein@google.com commit to alpha bitmap procs

The AutoRoll server is located here: https://autoroll-internal.skia.org/r/android-master-autoroll

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
be CC'd on the roll, and stop the roller if necessary.

Test: Presubmit checks will test this change.
Change-Id: I35d8f49ffafde9d8405bdf4222914ddbc01e6c87
Exempt-From-Owner-Approval: The autoroll bot does not require owner approval.