Get rid of all the library tags.

lib/src/backend/platform_selector/visitor.dart

 // Copyright (c) 2015, 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.
 
-library test.backend.platform_selector.visitor;
-
 import 'ast.dart';
 
 /// The interface for visitors of the platform selector AST.
 abstract class Visitor<T> {
   T visitVariable(VariableNode node);
   T visitNot(NotNode node);
   T visitOr(OrNode node);
   T visitAnd(AndNode node);
   T visitConditional(ConditionalNode node);
 }
@@ skipping 20 matching lines @@
     node.left.accept(this);
     node.right.accept(this);
   }
 
   void visitConditional(ConditionalNode node) {
     node.condition.accept(this);
     node.whenTrue.accept(this);
     node.whenFalse.accept(this);
   }
 }