Roll src/third_party/skia aa6ca0a8bfc1..74b6cf3a7215 (2 commits) (#7583)

https://skia.googlesource.com/skia.git/%2Blog/aa6ca0a8bfc1..74b6cf3a7215

git log aa6ca0a8bfc13050dfa3855fcaa6264586dd2b4b..74b6cf3a7215f62df002cf57685a12888950efcc --date=short --no-merges --format=%ad %ae %s
2019-01-25 skia-recreate-skps@skia-swarming-bots.iam.gserviceaccount.com Update go_deps asset
2019-01-25 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/swiftshader 6ab37b0f2ca0..86f8bdb2934c (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 (djsollen@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': 'aa6ca0a8bfc13050dfa3855fcaa6264586dd2b4b',
+  'skia_revision': '74b6cf3a7215f62df002cf57685a12888950efcc',
 
   # 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: 168c920ac24cbc3585110b2c748cf47e
+Signature: d68bfb7d611c1fba3baf92505429f3b6
 
 UNUSED LICENSES: