Roll Dart SDK from a2c9cae to ffbfa20 (1 revision) (#21031)

Author: skia-flutter-autoroll

DEPS

@@ -34,7 +34,7 @@ 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': 'a2c9cae4dcd802dd2c2972b981a27ee7a58f659f',
+  'dart_revision': 'ffbfa200043553be1fdfaedef497e185b90a416c',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py
@@ -193,7 +193,7 @@ deps = {
    Var('dart_git') + '/dart2js_info.git@0632a623b08e1f601c7eba99e0186a581ae799e9',
 
   'src/third_party/dart/third_party/pkg/dartdoc':
-   Var('dart_git') + '/dartdoc.git@291ebc50072746bc59ccab59115a298915218428',
+   Var('dart_git') + '/dartdoc.git@b039e21a7226b61ca2de7bd6c7a07fc77d4f64a9',
 
   'src/third_party/dart/third_party/pkg/ffi':
    Var('dart_git') + '/ffi.git@454ab0f9ea6bd06942a983238d8a6818b1357edb',

ci/licenses_golden/licenses_third_party

@@ -1,4 +1,4 @@
-Signature: cdd12c4e61799cb365d256582ce9a8c1
+Signature: d87258c3472783faf407d22721ce6725
 
 UNUSED LICENSES: