update completion sorter to new API

pkg/analysis_server/lib/src/services/completion/contribution_sorter.dart

Index: pkg/analysis_server/lib/src/services/completion/contribution_sorter.dart
diff --git a/pkg/analysis_server/lib/src/services/completion/contribution_sorter.dart b/pkg/analysis_server/lib/src/services/completion/contribution_sorter.dart
index 3d9dd87150df073c048ed868701a74199417c048..cc7b457ceb7ef0637f8a20cad536088884a3341a 100644
--- a/pkg/analysis_server/lib/src/services/completion/contribution_sorter.dart
+++ b/pkg/analysis_server/lib/src/services/completion/contribution_sorter.dart
@@ -6,6 +6,7 @@ library services.completion.sorter;
 
 import 'package:analysis_server/plugin/protocol/protocol.dart';
 import 'package:analysis_server/src/provisional/completion/completion_dart.dart';
+import 'package:analysis_server/src/provisional/completion/completion_core.dart';
 
 /**
  * The abstract class `ContributionSorter` defines the behavior of objects
@@ -17,10 +18,10 @@ abstract class ContributionSorter {
   /**
    * After [CompletionSuggestion]s have been computed,
    * this method is called to adjust the relevance of those suggestions.
-   * The compilation unit and completion node
-   * in the given completion context may not be resolved.
+   * Return an [AnalysisRequest] if more analysis is needed,
+   * or `null` if suggestion sorting is complete.
    * This method should execute quickly and not block.
    */
-  void sort(DartCompletionRequest request,
-      Iterable<CompletionSuggestion> suggestions);
+  AnalysisRequest sort(

[danrubel, 2015/11/13 21:03:46]

Although the default completion sorter needs no additional analysis, Luke's
dart-mind based completion sorter does, thus the sort method can return an
AnalysisRequest.

[Brian Wilkerson, 2015/11/14 16:59:24]

Doesn't that violate the requirement that "This method should execute quickly
and not block"?

Should "should" be replaced by "must"? What's the effect of implementing a
method that is slow or that has to wait for some analysis to complete?

[danrubel, 2015/11/17 06:58:45]

The current default sorter requires no additional analysis so I'm not worried in
the near to mid term.  Obviously any sorter that requests additional analysis
runs the risk of making completion non-performant. Allowing the sorter to
request additional analysis allows experimentation with the sorter
implementation (e.g. dart-mind), but we must vet any implementation before we
build it into the system.

+      CompletionRequest request, Iterable<CompletionSuggestion> suggestions);
 }