Roll Dart SDK from a15d19a0d914 to a3736d4e9b1b (1 revision) (flutter/engine#31397)

DEPS

@@ -39,7 +39,7 @@ vars = {
   # Dart is: https://github.com/dart-lang/sdk/blob/main/DEPS.
   # You can use //tools/dart/create_updated_flutter_deps.py to produce
   # updated revision list of existing dependencies.
-  'dart_revision': 'a15d19a0d914496874b19bc9597ac7745a0905b8',
+  'dart_revision': 'a3736d4e9b1b450eb9460295deee32a7a3d2d4a3',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py
@@ -214,7 +214,7 @@ deps = {
    Var('dart_git') + '/crypto.git@b5024e4de2b1c474dd558bef593ddbf0bfade152',
 
   'src/third_party/dart/third_party/pkg/csslib':
-   Var('dart_git') + '/csslib.git@158bfa94eed08c12c07a8ee0a3fded0ebdcd1fcb',
+   Var('dart_git') + '/csslib.git@f746368a0a53cf8f68fd71b218239034e88841d5',
 
   'src/third_party/dart/third_party/pkg/dartdoc':
    Var('dart_git') + '/dartdoc.git@b3927dd89d6ff9c78dc88ab2901e63b6a3bf29b7',
@@ -259,7 +259,7 @@ deps = {
    Var('dart_git') + '/matcher.git@07595a7739d47a8315caba5a8e58fb9ae3d81261',
 
   'src/third_party/dart/third_party/pkg/mime':
-   Var('dart_git') + '/mime.git@c931f4bed87221beaece356494b43731445ce7b8',
+   Var('dart_git') + '/mime.git@7f4252d469de032aa4df9f90e827dbac4b8efa48',
 
   'src/third_party/dart/third_party/pkg/mockito':
    Var('dart_git') + '/mockito.git@d39ac507483b9891165e422ec98d9fb480037c8b',