Roll src/third_party/dart 4ad5fab95753..439cabaec02f (2 commits) (flutter#15881)

https://dart.googlesource.com/sdk.git/+log/4ad5fab95753..439cabaec02f

git log 4ad5fab95753..439cabaec02f --date=short --first-parent --format='%ad %ae %s'
2020-01-22 rmacnak@google.com [test] Changes to mirrors tests to make them more Dart 3 compatible.
2020-01-22 markzipan@google.com [dartdevc] Adding support for function type object normalization.

Created with:
  gclient setdep -r src/third_party/dart@439cabaec02f

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/dart-sdk-flutter-engine
Please CC dart-vm-team@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

Bug: None
Tbr: dart-vm-team@google.com

Author: skia-flutter-autoroll

DEPS

@@ -34,7 +34,7 @@ vars = {
   # Dart is: https://github.com/dart-lang/sdk/blob/master/DEPS.
   # You can use //tools/dart/create_updated_flutter_deps.py to produce
   # updated revision list of existing dependencies.
-  'dart_revision': '4ad5fab957533f9f8ea8ec5fe8909d51ab674118',
+  'dart_revision': '439cabaec02f5d9f219f3d7d33ec29cad167863c',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py

ci/licenses_golden/licenses_third_party

@@ -1,4 +1,4 @@
-Signature: 4fbb5b275048bb6275f64687474729ad
+Signature: a581f97cf7b9a6d36324713c9bbc15d2
 
 UNUSED LICENSES: