Roll src/third_party/dart a6d06b59ec4b..4e520824f502 (7 commits) (#18276)

diff --git a/DEPS b/DEPS
index 915162a..613cef3 100644
--- a/DEPS
+++ b/DEPS
@@ -34,7 +34,7 @@
   # 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': 'a6d06b59ec4b65fefa173a25458fde6f098a3510',
+  'dart_revision': '4e520824f502f584b4ff05d2d7f8a9b07aa3fbc7',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py
diff --git a/ci/licenses_golden/licenses_third_party b/ci/licenses_golden/licenses_third_party
index 8718a4a..ec47026 100644
--- a/ci/licenses_golden/licenses_third_party
+++ b/ci/licenses_golden/licenses_third_party
@@ -1,4 +1,4 @@
-Signature: 684248f096ecaa2e7dd0406d347358d3
+Signature: 2f6992f71d20cae44f7d4af6b3c47d59
 
 UNUSED LICENSES: