update setAnalysisRoots to accept package spec file

pkg/analysis_server/tool/spec/generated/java/AnalysisServer.java

 /*
  * Copyright (c) 2015, 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 156 matching lines @@
    * but they will remain in the set of requested roots.
    *
    * If an included path represents a file, then server will look in the directory containing the
    * file for a pubspec.yaml file. If none is found, then the parents of the directory will be
    * searched until such a file is found or the root of the file system is reached. If such a file is
    * found, it will be used to resolve package: URI’s within the file.
    *
    * @param included A list of the files and directories that should be analyzed.
    * @param excluded A list of the files and directories within the included directories that should
    *         not be analyzed.
-   * @param packageRoots A mapping from source directories to target directories that should override
-   *         the normal package: URI resolution mechanism. The analyzer will behave as though each
-   *         source directory in the map contains a special pubspec.yaml file which resolves any
-   *         package: URI to the corresponding path within the target directory. The effect is the
-   *         same as specifying the target directory as a "--package_root" parameter to the Dart VM
-   *         when executing any Dart file inside the source directory. Files in any directories that
-   *         are not overridden by this mapping have their package: URI's resolved using the normal
+   * @param packageRoots A mapping from source directories to package roots that should override the
+   *         normal package: URI resolution mechanism. If a package root is a directory, then the
+   *         analyzer will behave as though the associated source directory in the map contains a
+   *         special pubspec.yaml file which resolves any package: URI to the corresponding path
+   *         within that package root directory. The effect is the same as specifying the package
+   *         root directory as a "--package_root" parameter to the Dart VM when executing any Dart
+   *         file inside the source directory. If a package root is a file, then the analyzer will
+   *         behave as though that file is a ".packages" file in the source directory. The effect is
+   *         the same as specifying the file as a "--packages" parameter to the Dart VM when
+   *         executing any Dart file inside the source directory. Files in any directories that are
+   *         not overridden by this mapping have their package: URI's resolved using the normal
    *         pubspec.yaml mechanism. If this field is absent, or the empty map is specified, that
    *         indicates that the normal pubspec.yaml mechanism should always be used.
    */
   public void analysis_setAnalysisRoots(List<String> included, List<String> excluded, Map<String, String> packageRoots);
 
   /**
    * {@code analysis.setGeneralSubscriptions}
    *
    * Subscribe for general services (that is, services that are not specific to individual files).
    * All previous subscriptions are replaced by the given set of services.
@@ skipping 377 matching lines @@
    * the response to this request has been sent.
    */
   public void server_shutdown();
 
   /**
    * Start the analysis server.
    */
   public void start() throws Exception;
 
 }