Roll external/skia 72d2f571ff2a..ea1b30b57b7b (5 commits)

https://skia.googlesource.com/skia.git/+log/72d2f571ff2a..ea1b30b57b7b

2019-09-19 robertphillips@google.com New proposed syntax for SkColorTypes
2019-09-19 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).
2019-09-19 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).
2019-09-19 robertphillips@google.com Alter wacky_yuv_formats GM to skip rows if the required backing GPU format(s) aren't supported
2019-09-19 robertphillips@google.com Remove "experimental" comments regarding RG_F16 and RGBA_16161616

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: I9b51f9f463a98fbc850d59027fe7f85f1844019a
Exempt-From-Owner-Approval: The autoroll bot does not require owner approval.