Roll src/third_party/skia d7a5a1d27e1d..50ea3c06b80f (9 commits) (#7688)

https://skia.googlesource.com/skia.git/%2Blog/d7a5a1d27e1d..50ea3c06b80f

git log d7a5a1d27e1d3ecc1ef4dfa1cef38195daf99f67..50ea3c06b80f7322c64fd99926edcdd7ea398213 --date=short --no-merges --format=%ad %ae %s
2019-02-04 brianosman@google.com Add support for MSVC run-time checks (and control flow guard)
2019-02-04 recipe-roller@chromium.org Roll recipe dependencies (trivial).
2019-02-04 halcanary@google.com SkPDF to use aliased em bounds.
2019-02-04 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/swiftshader 3f5a479280cc..612345523a8d (2 commits)
2019-02-04 reed@google.com templatize drawString
2019-02-04 egdaniel@google.com Minor clean ups to vulkan hardware buffer test.
2019-02-04 robertphillips@google.com Move GrContextOptions to GrContext_Base and make GrContextThreadSafeProxy be derived from GrContext_Base
2019-02-04 reed@google.com remove metadata from canvas
2019-01-31 herb@google.com Benchmark for charToGlyph

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 (fmalita@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': 'd7a5a1d27e1d3ecc1ef4dfa1cef38195daf99f67',
+  'skia_revision': '50ea3c06b80f7322c64fd99926edcdd7ea398213',
 
   # 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: f062937692335a9be503b3b81928e6ba
+Signature: 36c4a454b9ac0cbe7ed95735c8186d70
 
 UNUSED LICENSES:
 
@@ -1678,6 +1678,7 @@ FILE: ../../../third_party/skia/bench/JSONBench.cpp
 FILE: ../../../third_party/skia/bench/PathOpsBench.cpp
 FILE: ../../../third_party/skia/bench/PolyUtilsBench.cpp
 FILE: ../../../third_party/skia/bench/ShaderMaskFilterBench.cpp
+FILE: ../../../third_party/skia/bench/TypefaceBench.cpp
 FILE: ../../../third_party/skia/experimental/nima/NimaActor.cpp
 FILE: ../../../third_party/skia/experimental/nima/NimaActor.h
 FILE: ../../../third_party/skia/experimental/pvg/draw_msg.proto