Roll src/third_party/skia 4b203ad7ac02..9c71e7be1097 (4 commits) (#9353)

https://skia.googlesource.com/skia.git
/%2Blog/4b203ad7ac02..9c71e7be1097

git log 4b203ad7ac024b959fb6baa2d0cc3a724fb8fa85..9c71e7be1097a58a5918c1440a454def9388cff3 --date=short --no-merges --format=%ad %ae %s
2019-06-17 herb@google.com Remove all global mutexes
2019-06-17 mtklein@google.com enable SkVM JIT testing on x86-64 Linux bots
2019-06-17 mtklein@google.com centralize and force-inline unaligned_{load,store}
2019-06-17 csmartdalton@google.com Add a "preferredInternalSampleCount" cap

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 (bsalomon@google.com), and stop
the roller if necessary.

DEPS

@@ -24,7 +24,7 @@ vars = {
   'fuchsia_git': 'https://fuchsia.googlesource.com',
   'github_git': 'https://github.com',
   'skia_git': 'https://skia.googlesource.com',
-  'skia_revision': '4b203ad7ac024b959fb6baa2d0cc3a724fb8fa85',
+  'skia_revision': '9c71e7be1097a58a5918c1440a454def9388cff3',
 
   # 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: 65ab64b07144d3882a112a527a4d8572
+Signature: d456996d50ba426827d67a89abd2a4fb
 
 UNUSED LICENSES: