Roll external/skia 9a4a05e21..742319574 (2 commits)

https://skia.googlesource.com/skia.git/+log/9a4a05e21..742319574

2019-01-22 csmartdalton@google.com ccpr: Add explicit fmas to vertex placement code
2019-01-22 skia-recreate-skps@skia-swarming-bots.iam.gserviceaccount.com Update go_deps asset

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: I1425fc8d241b6ae981b919ed497a930d99ed0e0d
Exempt-From-Owner-Approval: The autoroll bot does not require owner approval.