Roll external/skia 1b1b65748..8ac78aa6d (1 commits)

https://skia.googlesource.com/skia.git/+log/1b1b65748..8ac78aa6d

2019-05-03 benjaminwagner@google.com Update the list of Skia dependencies

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: Ia77709eef42fd91777f39dff2125b6b376c0ebf0
Exempt-From-Owner-Approval: The autoroll bot does not require owner approval.