Use toList to copy lists and clean up errors and warnings

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

Index: pkg/analysis_server/lib/src/plugin/result_collector.dart
diff --git a/pkg/analysis_server/lib/src/plugin/result_collector.dart b/pkg/analysis_server/lib/src/plugin/result_collector.dart
index bb142842cdd378fc92f053f450796dfc2fb02776..d5491b97e91909489ccfa619d7a5e9dcd55a293b 100644
--- a/pkg/analysis_server/lib/src/plugin/result_collector.dart
+++ b/pkg/analysis_server/lib/src/plugin/result_collector.dart
@@ -49,7 +49,7 @@ class ResultCollector<E> {
    * 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>[];