Roll external/skia 8d64ee779..7077ae855 (18 commits)

https://skia.googlesource.com/skia.git/+log/8d64ee779..7077ae855

2017-10-05 reed@google.com remove legacy fontmgr flag from flutter
2017-10-05 angle-deps-roller@chromium.org Roll skia/third_party/externals/angle2/ 000dab88d..af143feff (1 commit)
2017-10-05 egdaniel@google.com When mip mapping, do YUV mip generation on CPU then upload to GPU.
2017-10-05 reed@google.com experiments to speed up drawing 32bit images into 565
2017-10-05 angle-deps-roller@chromium.org Roll skia/third_party/externals/angle2/ 63c5a5974..000dab88d (1 commit)
2017-10-05 bungeman@google.com Fewer atomic ops in debug with SkBufferHead.
2017-10-05 csmartdalton@google.com Revert "Attempt both GL and GLES for GPU unit tests"
2017-10-05 angle-deps-roller@chromium.org Roll skia/third_party/externals/angle2/ ce8602ab7..63c5a5974 (1 commit)
2017-10-05 mtklein@chromium.org clamp to [0,1] in all gradient tilers
2017-10-05 bungeman@google.com Clean up SkString reference counting a bit.
2017-10-05 csmartdalton@google.com Attempt both GL and GLES for GPU unit tests
2017-10-05 robertphillips@google.com Use draws instead of clears on Macs w/ Intel Iris Pro GPUs
2017-10-05 mtklein@chromium.org abort if glyph metrics fall outside safe rect
2017-10-05 mtklein@chromium.org reformat hard-to-read preprocessor in SkJumper.cpp
2017-10-05 ethannicholas@google.com converted GrConfigConversionEffect to SkSL
2017-10-05 caryclark@skia.org add constexpr to SkRect, SkIRect Make functions
2017-10-05 mtklein@chromium.org aggressively refactor pipeline building in SkColorSpaceXform
2017-10-05 mtklein@chromium.org disable object-size santizer in debug builds

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Change-Id: I4a4ab16de50d1ceb1ad87126590d6ef5a884e718
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