Update manager fixes to handle update check failures.

editor/tools/plugins/com.google.dart.tools.update.core/src/com/google/dart/tools/update/core/UpdateAdapter.java

 /*
  * Copyright (c) 2012, the Dart project authors.
  * 
  * Licensed under the Eclipse Public License v1.0 (the "License"); you may not use this file except
  * in compliance with the License. You may obtain a copy of the License at
  * 
  * http://www.eclipse.org/legal/epl-v10.html
  * 
  * Unless required by applicable law or agreed to in writing, software distributed under the License
  * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
  * or implied. See the License for the specific language governing permissions and limitations under
  * the License.
  */
 package com.google.dart.tools.update.core;
 
 /**
  * This adapter class provides default implementations for the methods described by the
  * {@link UpdateListener} interface.
  */
 public class UpdateAdapter implements UpdateListener {
 
   @Override
   public void checkComplete() {
   }
 
   @Override
+  public void checkFailed(String errorDetails) {
+  }
+
+  @Override
   public void checkStarted() {
   }
 
   @Override
   public void downloadCancelled() {
   }
 
   @Override
   public void downloadComplete() {
   }
@@ skipping 12 matching lines @@
 
   @Override
   public void updateAvailable(Revision revision) {
   }
 
   @Override
   public void updateStaged() {
   }
 
 }