Roll src/third_party/dart 7a94d1d7f1f2..86edfbef87b5 (1 commits) (#18463)

diff --git a/DEPS b/DEPS
index 7a71a8e..a0736b2 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': '7a94d1d7f1f24b2c5bb92ee8b4dec05d6a0ead0f',
+  'dart_revision': '86edfbef87b5207a48a0eff386f4dd48bf320f18',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py