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

dart/lib/compiler/implementation/universe/partial_type_tree.dart

 // 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.
 
-part of universe;
-
 class PartialTypeTree {
 
   final Compiler compiler;
   PartialTypeTreeNode root;
 
   // TODO(kasperl): This should be final but the VM will not allow
   // that without making the map a compile-time constant.
   Map<ClassElement, PartialTypeTreeNode> nodes =
       new Map<ClassElement, PartialTypeTreeNode>();
 
@@ skipping 153 matching lines @@
   bool visitRecursively(bool visit(PartialTypeTreeNode node)) {
     if (!visit(this)) return false;
     for (Link link = children; !link.isEmpty(); link = link.tail) {
       PartialTypeTreeNode child = link.head;
       if (!child.visitRecursively(visit)) return false;
     }
     return true;
   }
 
 }