Recompile unit with potential conflict/dependency on some top-level symbol.

compiler/java/com/google/dart/compiler/DartCompilerErrorCode.java

 // Copyright (c) 2011, 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.
 
 package com.google.dart.compiler;
 
 /**
  * Valid error codes for the errors produced by the Dart compiler.
  */
 public enum DartCompilerErrorCode implements ErrorCode {
@@ skipping 32 matching lines @@
 
   @Override
   public ErrorSeverity getErrorSeverity() {
     return severity;
   }
 
   @Override
   public SubSystem getSubSystem() {
     return SubSystem.COMPILER;
   }
+
+  @Override
+  public boolean needsRecompilation() {
+    return true;
+  }
 }