Revert "Manual roll Dart SDK from d6c08fa9bb54 to 6ff69d6b7f59 (15 revisions) (#49825)"

This reverts commit b33265d.

Author: auto-submit[bot]

DEPS

@@ -65,7 +65,7 @@ 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': '6ff69d6b7f5913ab52c97e072dfeac482d794113',
+  'dart_revision': 'd6c08fa9bb54dfc52e32ee879ae157f8a01d5a50',
 
   # 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_dart

@@ -1,4 +1,4 @@
-Signature: 7409de5fbfeb3a60d2310117fe55c60e
+Signature: 60ebc270fcd5313847ed98c6ce909e6a
 
 ====================================================================================================
 LIBRARY: dart
@@ -4707,7 +4707,7 @@ Exhibit B - "Incompatible With Secondary Licenses" Notice
   This Source Code Form is "Incompatible With Secondary Licenses", as
   defined by the Mozilla Public License, v. 2.0.
 
-You may obtain a copy of this library's Source Code Form from: https://dart.googlesource.com/sdk/+/6ff69d6b7f5913ab52c97e072dfeac482d794113
+You may obtain a copy of this library's Source Code Form from: https://dart.googlesource.com/sdk/+/d6c08fa9bb54dfc52e32ee879ae157f8a01d5a50
 /third_party/fallback_root_certificates/
 
 ====================================================================================================

sky/packages/sky_engine/LICENSE

@@ -31204,7 +31204,7 @@ Exhibit B - "Incompatible With Secondary Licenses" Notice
   This Source Code Form is "Incompatible With Secondary Licenses", as
   defined by the Mozilla Public License, v. 2.0.
 
-You may obtain a copy of this library's Source Code Form from: https://dart.googlesource.com/sdk/+/6ff69d6b7f5913ab52c97e072dfeac482d794113
+You may obtain a copy of this library's Source Code Form from: https://dart.googlesource.com/sdk/+/d6c08fa9bb54dfc52e32ee879ae157f8a01d5a50
 /third_party/fallback_root_certificates/
 
 --------------------------------------------------------------------------------