Use a poor man's incremental parser to perform incremental resolution.

pkg/analysis_server/lib/src/analysis_server.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 analysis.server;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analysis_server/src/analysis_logger.dart';
@@ skipping 925 matching lines @@
 
   /**
    * The controller for sending [ContextsChangedEvent]s.
    */
   StreamController<ContextsChangedEvent> _onContextsChangedController;
 
   ServerContextManager(this.analysisServer, ResourceProvider resourceProvider,
       PackageMapProvider packageMapProvider)
       : super(resourceProvider, packageMapProvider) {
     _onContextsChangedController = new StreamController<ContextsChangedEvent>();
+    defaultOptions.incremental = true;
   }
 
   /**
    * The stream that is notified when contexts are added or removed.
    */
   Stream<ContextsChangedEvent> get onContextsChanged =>
       _onContextsChangedController.stream;
 
   @override
   void addContext(Folder folder, UriResolver packageUriResolver) {
@@ skipping 43 matching lines @@
    * [packageUriResolver].
    */
   SourceFactory _createSourceFactory(UriResolver packageUriResolver) {
     List<UriResolver> resolvers = <UriResolver>[
         new DartUriResolver(analysisServer.defaultSdk),
         new ResourceUriResolver(resourceProvider),
         packageUriResolver];
     return new SourceFactory(resolvers);
   }
 }