Roll external/skia 4bcdb6b9a..b3043e4d7 (5 commits)

https://skia.googlesource.com/skia.git/+log/4bcdb6b9a..b3043e4d7

2019-05-30 herb@google.com Collapse the SkTextInterceptsIter into base class
2019-05-30 brianosman@google.com Interpreter: Elide dup/pop around stores
2019-05-30 bungeman@google.com Add trivial implemenations of shaper run iterators.
2019-05-30 rmistry@google.com Add new G3 compile try bot
2019-05-30 rmistry@google.com Add recipe for triggering and waiting for G3 compile tasks

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: I71cbfa85b46a08981c5ad0821b31e4ac66e47670
Exempt-From-Owner-Approval: The autoroll bot does not require owner approval.