Roll external/skia 4fea17393..4302eb9a6 (5 commits)

https://skia.googlesource.com/skia.git/+log/4fea17393..4302eb9a6

2018-10-04 mtklein@google.com Revert "remove deprecated SkRect::MakeFromIRect()"
2018-10-04 mtklein@google.com remove SkColorSpaceTransferFn::invert()
2018-10-04 brianosman@google.com Restore proper name of the SkImage_Gpu2Cpu unit test
2018-10-04 halcanary@google.com SK_SUPPORT_LEGACY_DOCUMENT_FACTORY: clean up part 2/2
2018-10-04 mtklein@google.com Reland "hash tf, and whole colorspace"

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Change-Id: Iec4a52d57a86b6f442eea4e79238df200e3eef8d
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