Roll src/third_party/skia 46f5ee156155..49ea3194535c (8 commits) (#8179)

https://skia.googlesource.com/skia.git/%2Blog/46f5ee156155..49ea3194535c

git log 46f5ee1561558857a1c669b43b71ca84f6ba6f22..49ea3194535c1783554149aab1d17f931512497e --date=short --no-merges --format=%ad %ae %s
2019-03-15 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/swiftshader f3b57974620d..1e6a9898b73b (1 commits)
2019-02-26 halcanary@google.com GN: split out skia_*_public from skia_*_sources
2019-03-15 robertphillips@google.com Reduce work done by GrYUVtoRGBEffect for kIdentity_SkYUVColorSpace
2019-03-15 halcanary@google.com Revert "Compile all fiddle examples locally"
2019-03-15 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/swiftshader 36411219ff2b..f3b57974620d (3 commits)
2019-03-15 brianosman@google.com Standardize naming on CoverageAsAlpha (rather than AlphaAsCoverage)
2019-03-08 bsalomon@google.com Revert "Revert "Distinguish between "flushed" and "finished" idle state callbacks on GrTexture.""
2019-03-15 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/swiftshader e37ce613d1c7..36411219ff2b (1 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 (benjaminwagner@google.com), and stop
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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': '46f5ee1561558857a1c669b43b71ca84f6ba6f22',
+  'skia_revision': '49ea3194535c1783554149aab1d17f931512497e',
 
   # When updating the Dart revision, ensure that all entries that are
   # dependencies of Dart are also updated to match the entries in the