Roll external/skia 8012a2f9f..a2187bf76 (15 commits)

https://skia.googlesource.com/skia.git/+log/8012a2f9f..a2187bf76

2018-11-16 mtklein@google.com port S32_alpha_D32_filter_DX to SkOpts
2018-11-16 caryclark@skia.org bookmaker error handling
2018-11-16 recipe-roller@chromium.org Roll recipe dependencies (trivial).
2018-11-16 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/angle2 c30f45d3f9c1..e4634a13a74d (5 commits)
2018-11-16 reed@google.com Reland "remove dead code around SK_SUPPORT_LEGACY_FONT_FLAGS"
2018-11-16 bsalomon@google.com Discard ops that don't have a finite bounds.
2018-11-16 bsalomon@google.com Fix dst copy bounds for aa draw contained within clip.
2018-11-16 mtklein@google.com there are no POSTAMBLEs
2018-11-16 herb@google.com Link SubRuns to Runs, and Runs to Blobs.
2018-11-16 reed@google.com Revert "remove SK_SUPPORT_LEGACY_NESTED_HINTINGENUM from flutter"
2018-11-16 reed@google.com Revert "remove dead code around SK_SUPPORT_LEGACY_FONT_FLAGS"
2018-11-16 reed@google.com remove dead code around SK_SUPPORT_LEGACY_FONT_FLAGS
2018-11-16 reed@google.com remove SK_SUPPORT_LEGACY_NESTED_HINTINGENUM from flutter
2018-11-16 csmartdalton@google.com Prefer GrAAConvexPathRenderer over ccpr
2018-11-16 jvanverth@google.com Revert "Remove use of integers for atlas indexing"

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: I935d260193a027f8dca18e6ff66350742e4b7dd6
Exempt-From-Owner-Approval: The autoroll bot does not require owner approval.