Addition of AnalysisServer.isSocketOpen for clients to know if the server is still running.

editor/tools/plugins/com.google.dart.server/src/com/google/dart/server/AnalysisServer.java

 /*
  * Copyright (c) 2014, 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
@@ skipping 337 matching lines @@
    * Subscribe for services. All previous subscriptions are replaced by the given set of services.
    *
    * It is an error if any of the elements in the list are not valid services. If there is an error,
    * then the current subscriptions will remain unchanged.
    *
    * @param subscriptions A list of the services being subscribed to.
    */
   public void execution_setSubscriptions(List<String> subscriptions);
 
   /**
+   * Return {@code true} if the socket is open.
+   */
+  public boolean isSocketOpen();
+
+  /**
    * Remove the given listener from the list of listeners that will receive notification when new
      * analysis results become available.
    *
    * @param listener the listener to be removed
    */
   public void removeAnalysisServerListener(AnalysisServerListener listener);
 
   /**
    * {@code search.findElementReferences}
    *
@@ skipping 88 matching lines @@
    * the response to this request has been sent.
    */
   public void server_shutdown();
 
   /**
    * Start the analysis server.
    */
   public void start() throws Exception;
 
 }