Add format API

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
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    * {@code completion.getSuggestions}
    *
    * Request that completion suggestions for the given offset in the given file be returned.
    *
    * @param file The file containing the point at which suggestions are to be made.
    * @param offset The offset within the file at which suggestions are to be made.
    */
   public void completion_getSuggestions(String file, int offset, GetSuggestionsConsumer consumer);
 
   /**
+   * {@code edit.format}
+   *
+   * Format the contents of a single file. The currently selected region of text is passed in so that
+   * the selection can be preserved across the formatting operation. The updated selection will be as
+   * close to matching the original as possible, but whitespace at the beginning or end of the
+   * selected region will be ignored.
+   *
+   * @param file The file containing the code to be formatted.
+   * @param selectionOffset The offset of the current selection in the file.
+   * @param selectionLength The length of the current selection in the file.
+   */
+  public void edit_format(String file, int selectionOffset, int selectionLength, FormatConsumer consumer);
+
+  /**
    * {@code edit.getAssists}
    *
    * Return the set of assists that are available at the given location. An assist is distinguished
    * from a refactoring primarily by the fact that it affects a single file and does not require user
    * input in order to be performed.
    *
    * @param file The file containing the code for which assists are being requested.
    * @param offset The offset of the code for which assists are being requested.
    * @param length The length of the code for which assists are being requested.
    */
@@ skipping 203 matching lines @@
    * the response to this request has been sent.
    */
   public void server_shutdown();
 
   /**
    * Start the analysis server.
    */
   public void start() throws Exception;
 
 }