(TBR) Fix failing tests

pkg/analyzer_cli/test/driver_test.dart

Index: pkg/analyzer_cli/test/driver_test.dart
diff --git a/pkg/analyzer_cli/test/driver_test.dart b/pkg/analyzer_cli/test/driver_test.dart
index 0a41705490760b8a763b1fe69f06fcce9420c3c4..b0875abb268095a5ede98d4c4414854cc1f79b92 100644
--- a/pkg/analyzer_cli/test/driver_test.dart
+++ b/pkg/analyzer_cli/test/driver_test.dart
@@ -298,7 +298,7 @@ linter:
                 ErrorSeverity.WARNING);
             // Should not be made fatal by `--fatal-warnings`.
             expect(outSink.toString(),
-                contains("[warning] The function 'baz' is not defined"));
+                contains("[warning] The function 'baz' isn't defined"));
             expect(
                 outSink.toString(), contains("1 error and 1 warning found."));
           });