Roll src/third_party/dart 2a3b844b41..8ab978b6d4 (7 commits)

dart-lang/sdk@8ab978b6d4 Flow analysis: remove unnecessary parameters from `conditional_*` methods.
dart-lang/sdk@c6a6220bfc Stop using LocalElement.visibleRange in refactorings.
dart-lang/sdk@8280a31ef0 Fix CREATE_LOCAL_VARIABLE for function typed variable.
dart-lang/sdk@a29261b553 Change MoveFileRefactoringImpl to use (already computed) resolved units.
dart-lang/sdk@eb066376c4 Migration: hook up flow analysis for boolean literals
dart-lang/sdk@a3b3dc00ca Migration: recategorize some tests.
dart-lang/sdk@2fda7f8002 [cfe] Handle qualified name as an AmbiguousBuilder.

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': '2a3b844b41e220e99870747f53ea4016169e7178',
+  'dart_revision': '8ab978b6d4f165aeb5c0b7655115adfe878309fa',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py