Roll src/third_party/skia b5c685991faa..42280f8961fa (32 commits) (#8535)

https://skia.googlesource.com/skia.git/%2Blog/b5c685991faa..42280f8961fa

git log b5c685991faa79d6ac5caeacd48644eca4954426..42280f8961fa90f5829b561f7925be3354e5991e --date=short --no-merges --format=%ad %ae %s
2019-04-10 brianosman@google.com Add Shared library Windows builds
2019-04-10 brianosman@google.com Even more DLL build fixes
2019-04-10 reed@google.com remove SkMixer, since we have explicit lerps/blends in SkShader
2019-04-10 egdaniel@google.com Reland "Remove unnecessary flush in RenderYUVAToRGBA (take 2)"
2019-04-10 fmalita@chromium.org [skottie] Initial "Levels" effect support
2019-04-10 fmalita@chromium.org Reland "[skottie] More snug kTop Shaper alignment"
2019-04-10 jvanverth@google.com Add mipmap generation for Metal
2019-04-10 halcanary@google.com SkPDF: narrow layer bbox
2019-04-10 egdaniel@google.com Revert "Remove unnecessary flush in RenderYUVAToRGBA (take 2)"
2019-04-10 mtklein@google.com make to_vec template parameters explicit
2019-04-10 mtklein@google.com tweak SkVx to play nicely with others
2019-04-08 herb@google.com Add an index to SkGlyphPos
2019-04-10 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).
2019-04-10 brianosman@google.com Make SkShaper's GN setup more DLL friendly
2019-04-10 brianosman@google.com Make Skottie's GN setup more DLL friendly
2019-04-10 ethannicholas@google.com moved files generated from .fp files into generated/ directories
2019-04-08 herb@google.com Reland "Do not use sub-pixel positioning for source space"
2019-04-10 robertphillips@google.com Remove unnecessary flush in RenderYUVAToRGBA (take 2)
2019-04-10 brianosman@google.com Delete SkSL::Compiler copy constructor and assignment operator
2019-04-10 bungeman@google.com Make path in Sk1DPathEffect thread safe.
2019-04-10 halcanary@google.com SkPDF: split GraphicStateStack out
2019-04-10 halcanary@google.com SkPDF: simplify device drawRect
2019-04-10 ethannicholas@google.com regenerated FP files to make bot happy
2019-04-09 bsalomon@google.com Add Vulkan implementation of transfering from GrSurface to a GrGpuBuffer
2019-04-10 brianosman@google.com Define all ImageSetEntry members out of line
2019-04-09 robertphillips@google.com Skip flush in GrDrawingManager if the specifed proxy doesn't have any work (take 2)
2019-04-09 rmistry@google.com [Android compile bot] Also build frameworks/base/libs/hwui
2019-04-09 nifong@google.com externs needed for cpu/gpu switch
2019-04-10 skia-recreate-skps@skia-swarming-bots.iam.gserviceaccount.com Update go_deps asset
2019-04-10 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/angle2 82418c821689..f39b4f0280ef (12 commits)
2019-04-10 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/swiftshader eba396cc66d3..f0aa9d5ab738 (14 commits)
2019-04-10 skia-autoroll@skia-public.iam.gserviceaccount.com Roll ../src 79154509c679..1b121674f584 (400 commits)

The AutoRoll server is located here: https://autoroll.skia.org/r/skia-flutter-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 (egdaniel@google.com), and stop
the roller if necessary.

DEPS

@@ -23,7 +23,7 @@ vars = {
   'fuchsia_git': 'https://fuchsia.googlesource.com',
   'github_git': 'https://github.com',
   'skia_git': 'https://skia.googlesource.com',
-  'skia_revision': 'b5c685991faa79d6ac5caeacd48644eca4954426',
+  'skia_revision': '42280f8961fa90f5829b561f7925be3354e5991e',
 
   # When updating the Dart revision, ensure that all entries that are
   # dependencies of Dart are also updated to match the entries in the