Replicate mock_sdk.dart in analyzer2dart package.

pkg/analyzer2dart/test/driver_test.dart

Index: pkg/analyzer2dart/test/driver_test.dart
diff --git a/pkg/analyzer2dart/test/driver_test.dart b/pkg/analyzer2dart/test/driver_test.dart
index 557a60895bfa47b495aac931955329ebc76e1491..f31379c1d984ed42a462300bb0d51fba50375fca 100644
--- a/pkg/analyzer2dart/test/driver_test.dart
+++ b/pkg/analyzer2dart/test/driver_test.dart
@@ -2,7 +2,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:analysis_testing/mock_sdk.dart';
+import 'mock_sdk.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';