Optimize top-level element declarations search.

pkg/analysis_server/lib/src/services/index/local_index.dart

 // Copyright (c) 2014, 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.
 
 library services.src.index.local_index;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/services/index/index.dart';
 import 'package:analysis_server/src/services/index/index_contributor.dart' as
@@ skipping 40 matching lines @@
    * is the `is-invoked-by` relationship, then the locations will be all of the
    * places where the function is invoked.
    */
   @override
   Future<List<Location>> getRelationships(Element element,
       Relationship relationship) {
     return _store.getRelationships(element, relationship);
   }
 
   @override
+  List<Element> getTopDeclarations(ElementNameFilter nameFilter) {
+    return _store.getTopDeclarations(nameFilter);
+  }
+
+  @override
   void indexHtmlUnit(AnalysisContext context, HtmlUnit unit) {
     contributors.indexHtmlUnit(_store, context, unit);
   }
 
   @override
   void indexUnit(AnalysisContext context, CompilationUnit unit) {
     contributors.indexDartUnit(_store, context, unit);
   }
 
   @override
@@ skipping 14 matching lines @@
   @override
   void run() {
     // NO-OP for the local index
   }
 
   @override
   void stop() {
     // NO-OP for the local index
   }
 }