Roll external/skia 26cedb4c603b..24feb5d28f0e (9 commits)

https://skia.googlesource.com/skia.git/+log/26cedb4c603b..24feb5d28f0e

2019-08-09 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).
2019-08-09 mtklein@google.com Revert "add a stub for running fiddles as GMs"
2019-08-09 robertphillips@google.com Add unit test to prevent future memory regressions
2019-08-09 senorblanco@chromium.org Dawn backend: first triangle.
2019-08-09 robertphillips@google.com Fix exactify for explicit resource allocation (take 2)
2019-08-09 mtklein@google.com add a stub for running fiddles as GMs
2019-08-09 halcanary@google.com experimental/editor: shape.h to unify all shaping code
2019-08-09 bungeman@google.com Correctly write out variable position.
2019-08-09 bsalomon@google.com Expose GrContext::dump() when SK_ENABLE_DUMP_GPU is defined.

The AutoRoll server is located here: https://skia-autoroll.corp.goog/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
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Bug: 138674523
Change-Id: I5e9c1f796f018461ff6940441b2ede3662047864