Capture more errors and improve duplicate error removal

pkg/analyzer/test/src/task/dart_test.dart

Index: pkg/analyzer/test/src/task/dart_test.dart
diff --git a/pkg/analyzer/test/src/task/dart_test.dart b/pkg/analyzer/test/src/task/dart_test.dart
index 7c02e2c9b12792856b10fd20e710031d944aaa00..9d826453d7d0123dc2dbb2eecede296a59356bf9 100644
--- a/pkg/analyzer/test/src/task/dart_test.dart
+++ b/pkg/analyzer/test/src/task/dart_test.dart
@@ -2104,6 +2104,7 @@ class LibraryUnitErrorsTaskTest extends _AbstractDartTaskTest {
       LibraryUnitErrorsTask.HINTS_INPUT,
       LibraryUnitErrorsTask.RESOLVE_REFERENCES_ERRORS_INPUT,
       LibraryUnitErrorsTask.RESOLVE_TYPE_NAMES_ERRORS_INPUT,
+      LibraryUnitErrorsTask.VARIABLE_REFERENCE_ERRORS_INPUT,
       LibraryUnitErrorsTask.VERIFY_ERRORS_INPUT
     ]));
   }