Create a new AstFactory class to be used by analyzer and its clients.

pkg/analyzer/lib/dart/ast/standard_ast_factory.dart

Index: pkg/analyzer/lib/dart/ast/standard_ast_factory.dart
diff --git a/pkg/analyzer/lib/dart/ast/standard_ast_factory.dart b/pkg/analyzer/lib/dart/ast/standard_ast_factory.dart
new file mode 100644
index 0000000000000000000000000000000000000000..9333242fd51ffbf4ef37a9ae7655191a7730fabe
--- /dev/null
+++ b/pkg/analyzer/lib/dart/ast/standard_ast_factory.dart
@@ -0,0 +1,11 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// 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:analyzer/dart/ast/ast_factory.dart';
+import 'package:analyzer/src/dart/ast/ast_factory.dart';
+
+/**
+ * Gets an instance of [AstFactory] based on the standard AST implementation.
+ */
+final AstFactory astFactory = new AstFactoryImpl();