Ground work for addition to new listener api

compiler/java/com/google/dart/compiler/DefaultDartCompilerListener.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;
 
+import com.google.dart.compiler.ast.DartUnit;
+
 /**
  * A default implementation of {@link DartCompilerListener} which counts
  * compilation errors.
  */
 public class DefaultDartCompilerListener extends DartCompilerListener {
 
   /**
    * The number of (fatal) problems that occurred during compilation.
    */
   private int problemCount = 0;
@@ skipping 76 matching lines @@
   protected void incrementWarningCount() {
     warningCount++;
   }
 
   /**
    * Increment the {@link #typeErrorCount} by 1
    */
   protected void incrementTypeErrorCount() {
     typeErrorCount++;
   }
+
+  @Override
+  public void unitCompiled(DartUnit unit) {
+  }
 }