Add support for built-in plugins

pkg/analysis_server/test/domain_completion_test.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 test.domain.completion;
 
 import 'dart:async';
 
 import 'package:analysis_server/protocol/protocol.dart';
 import 'package:analysis_server/protocol/protocol_generated.dart';
@@ skipping 690 matching lines @@
       assertNoResult('test');
     });
   }
 
   test_sentToPlugins() async {
     addTestFile('''
       void main() {
         ^
       }
     ''');
-    PluginInfo info = new PluginInfo('a', 'b', 'c', null, null);
+    PluginInfo info = new DiscoveredPluginInfo('a', 'b', 'c', null, null);
     plugin.CompletionGetSuggestionsResult result =
         new plugin.CompletionGetSuggestionsResult(
             1, 2, <plugin.CompletionSuggestion>[
       new plugin.CompletionSuggestion(
           plugin.CompletionSuggestionKind.IDENTIFIER,
           DART_RELEVANCE_DEFAULT,
           'plugin completion',
           3,
           0,
           false,
@@ skipping 55 matching lines @@
 
   @override
   Future sort(
       CompletionRequest request, Iterable<CompletionSuggestion> suggestions) {
     if (!enabled) {
       throw 'unexpected sort';
     }
     return new Future.value();
   }
 }