Roll external/skia 07f93f299..44764000b (7 commits)

https://skia.googlesource.com/skia.git/+log/07f93f299..44764000b

2018-11-14 scroggo@google.com Add SafetyNetLogging and use in SkPngCodec
2018-11-14 bsalomon@google.com Reenable GrOp chaining.
2018-11-14 mtklein@google.com Revert "remove Clamp_S32_opaque_D32_nofilter_DX_shaderproc"
2018-11-14 reed@google.com don't use nested form of FontMetrics
2018-11-14 mtklein@google.com remove Clamp_S32_opaque_D32_nofilter_DX_shaderproc
2018-11-14 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/angle2 d1a55e393e65..fca8fd620190 (2 commits)
2018-11-14 benjaminwagner@google.com Add client code search to docs.

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
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Bug: 117838472
Change-Id: If10797ddc74d4117e5dfc2b396bdb54a7bb0e068