Roll Dart SDK from 9704370488b0 to e778310fcdcc (1 revision) (#25466)

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': '9704370488b010bb3dcbae0841615feb54e5c5e8',
+  'dart_revision': 'e778310fcdcc387c9201388b23d71a83ab5f3d0a',
 
   # 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

-Signature: e38f139402ef9b82fa4c39aef844ae30
+Signature: cfc21bffde83c392d2778396203ed0f7
 
 UNUSED LICENSES: