Specify when 'sortMembers' will return an error.

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 08e5feffc41654f632cf2d8645c4b12b2bbceb02..b274b2dfd3aa28d4d39de96cb087722d8f839ba2 100644
--- a/pkg/analysis_server/test/integration/integration_test_methods.dart
+++ b/pkg/analysis_server/test/integration/integration_test_methods.dart
@@ -1204,6 +1204,13 @@ abstract class IntegrationTestMixin {
   /**
    * Sort all of the directives, unit and class members of the given Dart file.
    *
+   * If a request is made for a file that does not exist, does not belong to an
+   * analysis root or is not a Dart file, SORT_MEMBERS_INVALID_FILE will be
+   * generated.
+   *
+   * If the Dart file has scan or parse errors, SORT_MEMBERS_PARSE_ERRORS will
+   * be generated.
+   *
    * Parameters
    *
    * file ( FilePath )