Optimize top-level element declarations search.

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

Index: pkg/analysis_server/lib/src/services/index/index_store.dart
diff --git a/pkg/analysis_server/lib/src/services/index/index_store.dart b/pkg/analysis_server/lib/src/services/index/index_store.dart
index a3f1950f5943e8f4cfd9911e3fb180160e17b8f1..58f543aa5e10d8d4687cd6de020619b1a10e22b3 100644
--- a/pkg/analysis_server/lib/src/services/index/index_store.dart
+++ b/pkg/analysis_server/lib/src/services/index/index_store.dart
@@ -84,6 +84,11 @@ abstract class IndexStore {
       Relationship relationship);
 
   /**
+   * Returns top-level [Element]s whose names satisfy to [nameFilter].
+   */
+  List<Element> getTopLevelDeclarations(ElementNameFilter nameFilter);
+
+  /**
    * Records that the given [element] and [location] have the given
    * [relationship].
    *
@@ -110,6 +115,11 @@ abstract class IndexStore {
       Location location);
 
   /**
+   * Records the declaration of the given top-level [element].
+   */
+  void recordTopDeclaration(Element element);
+
+  /**
    * Removes from the index all of the information associated with [context].
    *
    * This method should be invoked when [context] is disposed.