Fix error handling for formatting and update the spec

pkg/analysis_server/test/integration/integration_test_methods.dart

Index: pkg/analysis_server/test/integration/integration_test_methods.dart
diff --git a/pkg/analysis_server/test/integration/integration_test_methods.dart b/pkg/analysis_server/test/integration/integration_test_methods.dart
index 86879e6aabf8a4082e8a243e00b811515f68555e..eba2bda6f09db8083963a1f5d9c2ae2e8c2426fe 100644
--- a/pkg/analysis_server/test/integration/integration_test_methods.dart
+++ b/pkg/analysis_server/test/integration/integration_test_methods.dart
@@ -1073,7 +1073,8 @@ abstract class IntegrationTestMixin {
    * If a request is made for a file which does not exist, or which is not
    * currently subject to analysis (e.g. because it is not associated with any
    * analysis root specified to analysis.setAnalysisRoots), an error of type
-   * FORMAT_INVALID_FILE will be generated.
+   * FORMAT_INVALID_FILE will be generated. If the source contains syntax
+   * errors, an error of type FORMAT_WITH_ERRORS will be generated.
    *
    * Parameters
    *