Keep known valid Dart results and invalidate all the other results during incremental resolution.

pkg/analyzer/lib/src/context/cache.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.context.cache;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/src/generated/engine.dart'
@@ skipping 523 matching lines @@
     if (deltaResult == DeltaResult.KEEP_CONTINUE) {
       thisData = _resultMap[descriptor];
     }
     if (thisData == null) {
       return;
     }
     // Stop depending on other results.
     TargetedResult thisResult = new TargetedResult(target, descriptor);
     for (TargetedResult dependedOnResult in thisData.dependedOnResults) {
       ResultData data = _partition._getDataFor(dependedOnResult);
-      if (data != null) {
+      if (data != null && deltaResult != DeltaResult.KEEP_CONTINUE) {
         data.dependentResults.remove(thisResult);
       }
     }
     // Invalidate results that depend on this result.
     List<TargetedResult> dependentResults = thisData.dependentResults.toList();
     for (TargetedResult dependentResult in dependentResults) {
       CacheEntry entry = _partition.get(dependentResult.target);
       if (entry != null) {
         entry._invalidate(dependentResult.result, delta);
       }
@@ skipping 589 matching lines @@
   void resultAccessed(TargetedResult result) {}
 
   @override
   List<TargetedResult> resultStored(TargetedResult newResult, newValue) {
     return TargetedResult.EMPTY_LIST;
   }
 
   @override
   void targetRemoved(AnalysisTarget target) {}
 }