Adapt the existing incremental resolution implementation to the new model.

pkg/analyzer/lib/src/task/dart_work_manager.dart

 // Copyright (c) 2015, 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 analyzer.src.task.dart_work_manager;
 
 import 'dart:collection';
 
 import 'package:analyzer/src/context/cache.dart';
 import 'package:analyzer/src/generated/engine.dart'
@@ skipping 224 matching lines @@
   WorkOrderPriority getNextResultPriority() {
     if (priorityResultQueue.isNotEmpty) {
       return WorkOrderPriority.PRIORITY;
     }
     if (unknownSourceQueue.isNotEmpty || librarySourceQueue.isNotEmpty) {
       return WorkOrderPriority.NORMAL;
     }
     return WorkOrderPriority.NONE;
   }
 
+  void unitIncrementallyResolved(Source librarySource, Source unitSource) {
+    librarySourceQueue.add(librarySource);
+  }
+
   @override
   void resultsComputed(
       AnalysisTarget target, Map<ResultDescriptor, dynamic> outputs) {
     // Organize sources.
     if (_isDartSource(target)) {
       SourceKind kind = outputs[SOURCE_KIND];
       if (kind != null) {
         unknownSourceQueue.remove(target);
         if (kind == SourceKind.LIBRARY) {
           librarySourceQueue.add(target);
@@ skipping 78 matching lines @@
 
   static bool _isDartSource(AnalysisTarget target) {
     return target is Source && AnalysisEngine.isDartFileName(target.fullName);
   }
 
   static bool _isErrorResult(ResultDescriptor descriptor) {
     return _SOURCE_ERRORS.contains(descriptor) ||
         _UNIT_ERRORS.contains(descriptor);
   }
 }