Revert "Parts must start with 'part of'" and "Attempt to fix VM build"

dart/pkg/dartdoc/lib/src/markdown/ast.dart

Index: dart/pkg/dartdoc/lib/src/markdown/ast.dart
diff --git a/dart/pkg/dartdoc/lib/src/markdown/ast.dart b/dart/pkg/dartdoc/lib/src/markdown/ast.dart
index 96cbdc987d163d7dfdbe68edf4accf7f9786da40..103e46dabb454ae156daa5518b8e736c64f3f0b3 100644
--- a/dart/pkg/dartdoc/lib/src/markdown/ast.dart
+++ b/dart/pkg/dartdoc/lib/src/markdown/ast.dart
@@ -1,5 +1,3 @@
-part of markdown;
-
 // Copyright (c) 2012, 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.