Roll Dart SDK from 5acaa5f to cfaa760 (2 revisions) (#22827)

Author: skia-flutter-autoroll

DEPS

@@ -34,11 +34,10 @@ 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': '5acaa5f14b03a1d3711c91bc4ee9a24f3e21a299',
+  'dart_revision': 'cfaa7606cbf5fa53c6d228d655734d6de002b052',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py
-  'dart_args_tag': '1.6.0',
   'dart_boringssl_gen_rev': '429ccb1877f7987a6f3988228bc2440e61293499',
   'dart_boringssl_rev': '4dfd5af70191b068aebe567b8e29ce108cee85ce',
   'dart_clock_rev': 'a494269254ba978e7ef8f192c5f7fec3fc05b9d3',
@@ -157,7 +156,7 @@ deps = {
   # WARNING: Unused Dart dependencies in the list below till "WARNING:" marker are removed automatically - see create_updated_flutter_deps.py.
 
   'src/third_party/dart/third_party/pkg/args':
-   Var('dart_git') + '/args.git' + '@' + Var('dart_args_tag'),
+   Var('dart_git') + '/args.git@139140125126661fac88c9aa5882165936d01c91',
 
   'src/third_party/dart/third_party/pkg/async':
    Var('dart_git') + '/async.git@695b3ac280f107c84adf7488743abfdfaaeea68f',

ci/licenses_golden/licenses_third_party

@@ -1,4 +1,4 @@
-Signature: c1012bf0b8370977d0de2888292a72b2
+Signature: c95a6daa96fa8983da2bce1cd4d5eb16
 
 UNUSED LICENSES:
 

tools/const_finder/.dart_tool/package_config.json

@@ -23,7 +23,7 @@
       "name": "args",
       "rootUri": "../../../../third_party/dart/third_party/pkg/args",
       "packageUri": "lib",
-      "languageVersion": "2.3"
+      "languageVersion": "2.12"
     },
     {
       "name": "collection",