Implement SearchEngine.searchAllSubtypes() with the analysis driver.

pkg/analysis_server/lib/src/services/search/search_engine_internal2.dart

Index: pkg/analysis_server/lib/src/services/search/search_engine_internal2.dart
diff --git a/pkg/analysis_server/lib/src/services/search/search_engine_internal2.dart b/pkg/analysis_server/lib/src/services/search/search_engine_internal2.dart
index 04dd6c59e9220d1eea6ce397ff65b3cae2b1cc8b..71b1f297063883b485648ae119faada1bb663c45 100644
--- a/pkg/analysis_server/lib/src/services/search/search_engine_internal2.dart
+++ b/pkg/analysis_server/lib/src/services/search/search_engine_internal2.dart
@@ -19,9 +19,21 @@ class SearchEngineImpl2 implements SearchEngine {
   SearchEngineImpl2(this._drivers);
 
   @override
-  Future<List<SearchMatch>> searchAllSubtypes(ClassElement type) async {
-    // TODO(scheglov) implement
-    return [];
+  Future<Set<ClassElement>> searchAllSubtypes(ClassElement type) async {
+    Set<ClassElement> allSubtypes = new Set<ClassElement>();
+
+    Future<Null> addSubtypes(ClassElement type) async {
+      List<SearchResult> directResults = await _searchDirectSubtypes(type);
+      for (SearchResult directResult in directResults) {
+        var directSubtype = directResult.enclosingElement as ClassElement;
+        if (allSubtypes.add(directSubtype)) {
+          await addSubtypes(directSubtype);
+        }
+      }
+    }
+
+    await addSubtypes(type);
+    return allSubtypes;
   }
 
   @override
@@ -48,12 +60,8 @@ class SearchEngineImpl2 implements SearchEngine {
 
   @override
   Future<List<SearchMatch>> searchSubtypes(ClassElement type) async {
-    List<SearchResult> allResults = [];
-    for (AnalysisDriver driver in _drivers) {
-      List<SearchResult> results = await driver.search.subTypes(type);
-      allResults.addAll(results);
-    }
-    return allResults.map(_SearchMatch.forSearchResult).toList();
+    List<SearchResult> results = await _searchDirectSubtypes(type);
+    return results.map(_SearchMatch.forSearchResult).toList();
   }
 
   @override
@@ -61,6 +69,15 @@ class SearchEngineImpl2 implements SearchEngine {
     // TODO(scheglov) implement
     return [];
   }
+
+  Future<List<SearchResult>> _searchDirectSubtypes(ClassElement type) async {
+    List<SearchResult> allResults = [];
+    for (AnalysisDriver driver in _drivers) {
+      List<SearchResult> results = await driver.search.subTypes(type);
+      allResults.addAll(results);
+    }
+    return allResults;
+  }
 }
 
 class _SearchMatch implements SearchMatch {