Roll Dart SDK from 996a58122821 to 9542c7bc569a (3 revisions) (#23463)

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': '996a581228215f7db426a18c2f003078138b87cb',
+  'dart_revision': '9542c7bc569aedd82fc626a53274c10d9033002a',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py
@@ -183,7 +183,7 @@ deps = {
    Var('dart_git') + '/crypto.git@c89a5be0375875fe7ff71625fa2b79f5a421f06d',
 
   'src/third_party/dart/third_party/pkg/csslib':
-   Var('dart_git') + '/csslib.git@6f77b3dcee957d3e2d5083f666221a220e9ed1f1',
+   Var('dart_git') + '/csslib.git@e411d862fd8cc50415c1badf2632e017373b3f47',
 
   'src/third_party/dart/third_party/pkg/dart2js_info':
    Var('dart_git') + '/dart2js_info.git@e0acfeb5affdf94c53067e68bd836adf589628fd',

ci/licenses_golden/licenses_third_party

-Signature: d3b14917ea726cd3cf6eca85b735025e
+Signature: 950125c44186e46466089663fd97582c
 
 UNUSED LICENSES: