Use toList to copy lists and clean up errors and warnings

pkg/analysis_server/lib/src/plugin/result_collector.dart

 // Copyright (c) 2017, 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.
 
 /**
  * An object used to collect partial results (of type [E]) where the partial
  * results are contributed by plugins.
  */
 class ResultCollector<E> {
   /**
@@ skipping 31 matching lines @@
   void clearResultsFromPlugin(String pluginId) {
     for (Map<String, E> partialResults in resultMap.values) {
       partialResults.remove(pluginId);
     }
   }
 
   /**
    * Return an iterator producing the partial results that have been contributed
    * for the given [filePath].
    */
-  Iterable<E> getResults(String filePath) {
+  List<E> getResults(String filePath) {
     Map<String, E> partialResultMap = resultMap[filePath];
     if (partialResultMap == null) {
       return <E>[];
     }
     List<E> values = partialResultMap.values.toList();
     //
     // Ensure that the server's contributions are always first in the list.
     //
     E serverContributions = partialResultMap[serverId];
     if (serverContributions != null && values.remove(serverContributions)) {
@@ skipping 24 matching lines @@
 
   /**
    * Stop collecting results contributed for the file with the given [filePath].
    * Until the collector is told to start collecting results for the file, any
    * results that are contributed for the file are discarded.
    */
   void stopCollectingFor(String filePath) {
     resultMap.remove(filePath);
   }
 }