Break up another large file

pkg/analysis_server/test/plugin/protocol_dart_test.dart

Index: pkg/analysis_server/test/plugin/protocol_dart_test.dart
diff --git a/pkg/analysis_server/test/plugin/protocol_dart_test.dart b/pkg/analysis_server/test/plugin/protocol_dart_test.dart
index 8920e92078fa10a2687235b7f7fa4044dfe1564b..ef2cd5089f09765e73821548688ef151f7bb8257 100644
--- a/pkg/analysis_server/test/plugin/protocol_dart_test.dart
+++ b/pkg/analysis_server/test/plugin/protocol_dart_test.dart
@@ -10,9 +10,10 @@ import 'package:analyzer/dart/ast/ast.dart' as engine;
 import 'package:analyzer/dart/ast/visitor.dart' as engine;
 import 'package:analyzer/dart/element/element.dart' as engine;
 import 'package:analyzer/dart/element/type.dart' as engine;
+import 'package:analyzer/error/error.dart' as engine;
 import 'package:analyzer/src/dart/ast/utilities.dart' as engine;
 import 'package:analyzer/src/dart/element/element.dart' as engine;
-import 'package:analyzer/src/generated/error.dart' as engine;
+import 'package:analyzer/src/error/codes.dart' as engine;
 import 'package:analyzer/src/generated/source.dart' as engine;
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 import 'package:unittest/unittest.dart';