Manual roll of Dart 1a18fff...ba80ed9 (flutter#22216)

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': 'ba80ed989cc94e266bf3939b9c3422d564227b0f',
+  'dart_revision': '1a18fff9ad2ee79095f8b92d76f714cb666a3384',
 
   # 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_third_party

@@ -1,4 +1,4 @@
-Signature: c7b3b09f8e57e8e336788e790a01ba6f
+Signature: 0d0465ed6c5853c039e190f5d7211240
 
 UNUSED LICENSES:
 

testing/scenario_app/lib/src/channel_util.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.6
+
 import 'dart:convert';
 import 'dart:ui';
 

testing/scenario_app/lib/src/locale_initialization.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.6
+
 import 'dart:typed_data';
 import 'dart:ui';
 

testing/scenario_app/lib/src/send_text_focus_semantics.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.6
+
 import 'dart:typed_data';
 import 'dart:ui';
 

testing/scenario_app/lib/src/touches_scenario.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.6
+
 import 'dart:convert';
 import 'dart:ui';