Roll src/third_party/dart ecd82166c312..b560016446e7 (1 commits) (#18450)

diff --git a/DEPS b/DEPS
index ad1fa55..8ad15c9 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': 'ecd82166c31297db61f062c9ba509a2d498d6cef',
+  'dart_revision': 'b560016446e7bdc55eb533e726b6c02afdbfc3ff',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py