filter imported element suggestions to reduce number of results sent to client

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

Index: pkg/analysis_server/lib/src/services/completion/dart_completion_manager.dart
diff --git a/pkg/analysis_server/lib/src/services/completion/dart_completion_manager.dart b/pkg/analysis_server/lib/src/services/completion/dart_completion_manager.dart
index e2c9cdcbf525a25f5c5e87147931e61e3f6897fc..99dc408a6155a4af55f3d9e45fee5a6fd61cab74 100644
--- a/pkg/analysis_server/lib/src/services/completion/dart_completion_manager.dart
+++ b/pkg/analysis_server/lib/src/services/completion/dart_completion_manager.dart
@@ -265,6 +265,14 @@ class DartCompletionRequest extends CompletionRequest {
    */
   final List<CompletionSuggestion> suggestions = <CompletionSuggestion>[];
 
+  /**
+   * Return the original text from the [replacementOffset] to the [offset]
+   * that can be used to filter the suggestions on the server side.
+   */
+  String get filterText {
+    return context.getContents(source).data.substring(replacementOffset, offset);
+  }
+
   DartCompletionRequest(this.context, this.searchEngine, this.source,
       int offset, this.cache, CompletionPerformance performance)
       : super(offset, performance);