Roll src/third_party/skia 42280f8961fa..99d792276740 (8 commits) (#8539)

https://skia.googlesource.com/skia.git/%2Blog/42280f8961fa..99d792276740

git log 42280f8961fa90f5829b561f7925be3354e5991e..99d792276740293109edb22a26fea50490e7eeaf --date=short --no-merges --format=%ad %ae %s
2019-04-10 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).
2019-04-10 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).
2019-04-10 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).
2019-04-10 reed@google.com oops, remove the rest of SkMixer
2019-04-10 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).
2019-04-10 herb@google.com Return a span from getMetrics
2019-04-10 egdaniel@google.com Add more general flush call to GrContext.
2019-04-10 ethannicholas@google.com removed duplicate GrCircleEffect.cpp

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': '42280f8961fa90f5829b561f7925be3354e5991e',
+  'skia_revision': '99d792276740293109edb22a26fea50490e7eeaf',
 
   # When updating the Dart revision, ensure that all entries that are
   # dependencies of Dart are also updated to match the entries in the

ci/licenses_golden/licenses_skia

-Signature: 33cde79edb8f35f77d8b871b39c8ca91
+Signature: 694d7fba29996869dade20431a948972
 
 UNUSED LICENSES:
 
@@ -4417,7 +4417,6 @@ FILE: ../../../third_party/skia/src/gpu/ccpr/GrGSCoverageProcessor.cpp
 FILE: ../../../third_party/skia/src/gpu/ccpr/GrVSCoverageProcessor.cpp
 FILE: ../../../third_party/skia/src/gpu/effects/GrAtlasedShaderHelpers.h
 FILE: ../../../third_party/skia/src/gpu/effects/GrBlurredEdgeFragmentProcessor.fp
-FILE: ../../../third_party/skia/src/gpu/effects/GrCircleEffect.cpp
 FILE: ../../../third_party/skia/src/gpu/effects/GrCircleEffect.fp
 FILE: ../../../third_party/skia/src/gpu/effects/GrCircleEffect.h
 FILE: ../../../third_party/skia/src/gpu/effects/GrEllipseEffect.fp