One more fix for making removing overlays incremental changes.

pkg/analyzer/test/src/context/context_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.src.context.context_test;
 
 import 'dart:async';
 
 import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:analyzer/src/cancelable_future.dart';
@@ skipping 290 matching lines @@
     // add overlay
     context.setContents(source, r'''
 main() {
   print(12);
 }
 ''');
     _analyzeAll_assertFinished();
     expect(context.getResolvedCompilationUnit2(source, source), unit);
     // remove overlay
     context.setContents(source, null);
+    context.validateCacheConsistency();
     _analyzeAll_assertFinished();
     expect(context.getResolvedCompilationUnit2(source, source), unit);
   }
 
   Future test_applyChanges_removeContainer() {
     SourcesChangedListener listener = new SourcesChangedListener();
     context.onSourcesChanged.listen(listener.onData);
     String libAContents = r'''
 library libA;
 import 'libB.dart';''';
@@ skipping 1984 matching lines @@
   }
 }
 
 class _AnalysisContextImplTest_test_applyChanges_removeContainer
     implements SourceContainer {
   Source libB;
   _AnalysisContextImplTest_test_applyChanges_removeContainer(this.libB);
   @override
   bool contains(Source source) => source == libB;
 }