Roll Dart SDK from 624322b to 4f1a93c (2 revisions)

https://dart.googlesource.com/sdk.git/+log/624322b41ddb..4f1a93c0cd09

2021-06-25 dart-luci-ci-builder@dart-ci.iam.gserviceaccount.com Version 2.14.0-249.0.dev
2021-06-25 dart-luci-ci-builder@dart-ci.iam.gserviceaccount.com Version 2.14.0-248.0.dev

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/+doc/main/autoroll/README.md

Author: skia-flutter-autoroll

DEPS

@@ -35,7 +35,7 @@ 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': '624322b41ddb1bd0049f375d5a36b40b5575ce27',
+  'dart_revision': '4f1a93c0cd09e946470828fb7cdabd63f92bf136',
 
   # 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: 1187c5e921874341e18d94a1612734b7
+Signature: 69aff763650048cdf9ddd351a34769bb
 
 UNUSED LICENSES:
 
@@ -9936,6 +9936,7 @@ FILE: ../../../third_party/dart/samples/ffi/resource_management/utf8_helpers.dar
 FILE: ../../../third_party/dart/samples_2/ffi/resource_management/utf8_helpers.dart
 FILE: ../../../third_party/dart/sdk/lib/_internal/js_runtime/lib/late_helper.dart
 FILE: ../../../third_party/dart/sdk/lib/_internal/vm/lib/ffi_allocation_patch.dart
+FILE: ../../../third_party/dart/sdk/lib/core/enum.dart
 FILE: ../../../third_party/dart/sdk/lib/ffi/allocation.dart
 FILE: ../../../third_party/dart/sdk/lib/ffi/union.dart
 ----------------------------------------------------------------------------------------------------