Roll external/skia a8a851bc5..60ad17593 (16 commits)

https://skia.googlesource.com/skia.git/+log/a8a851bc5..60ad17593

2018-10-18 recipe-roller@chromium.org Roll recipe dependencies (trivial).
2018-10-18 mtklein@google.com re-enable effect deserialization for flutter
2018-10-18 brianosman@google.com Add bitmap-as-shader case to P3 GM
2018-10-18 egdaniel@google.com Add function support for vulkan ycbcr conversion.
2018-10-18 herb@google.com Blacklist dftext
2018-10-18 brianosman@google.com Return texture color space when converting raster images to proxies
2018-10-18 fmalita@chromium.org Trim SkPictureShader's key
2018-10-18 skia-autoroll@skia-public.iam.gserviceaccount.com Roll skia/third_party/skcms f3e50cfac5bc..1ce6da5c8d99 (1 commits)
2018-10-18 bsalomon@google.com Validate allocation size in GrBufferAllocPool using SkSafeMath.
2018-10-18 scroggo@google.com Properly fill in memory in sampled RLE BMPs
2018-10-18 kjlubick@google.com Add Bloaty (with demangling) for wasm BuildStats
2018-10-18 mtklein@google.com split out effect deserialization, disable in flutter
2018-10-18 herb@google.com Simplify atlas calculation for dimension only
2018-10-18 jvanverth@google.com Reland: Widen internal API to support more complex YUV formats
2018-10-18 recipe-roller@chromium.org Roll recipe dependencies (trivial).
2018-10-18 scroggo@google.com Blacklist PNGs with CRC errors when using platform

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: Ie088f55e258e1a6be6f773da6f2ca7bf0dd5ab4a
Exempt-From-Owner-Approval: The autoroll bot does not require owner approval.