Try to use incremental resolution after removing overlays.

pkg/analyzer/test/generated/engine_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.
 
 // This code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library engine.engine_test;
 
 import 'dart:async';
 import 'dart:collection';
 
+import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:analyzer/src/cancelable_future.dart';
 import 'package:analyzer/src/context/cache.dart' show CacheEntry;
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/constant.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/html.dart' as ht;
 import 'package:analyzer/src/generated/java_core.dart';
 import 'package:analyzer/src/generated/java_engine.dart';
@@ skipping 417 matching lines @@
       listener.assertEvent(wereSourcesAdded: true);
       listener.assertEvent(changedSources: [libA]);
       listener.assertEvent(wereSourcesAdded: true);
       listener.assertEvent(changedSources: [libB]);
       listener.assertEvent(changedSources: [libB]);
       listener.assertEvent(wereSourcesRemovedOrDeleted: true);
       listener.assertNoMoreEvents();
     });
   }
 
+  /**
+   * IDEA uses the following scenarion:

[Brian Wilkerson, 2015/07/06 16:14:41]

"scenarion" --> "scenario"

+   * 1. Add overlay.
+   * 2. Change overlay.
+   * 3. If the contents of the document buffer is the same as the contents
+   *    of the file, remove overlay.
+   * So, we need to try to use incremental resolution for removing overlays too.
+   */
+  void test_applyChanges_remove_incremental() {
+    MemoryResourceProvider resourceProvider = new MemoryResourceProvider();
+    Source source = resourceProvider.newFile('/test.dart', r'''
+main() {
+  print(1);
+}
+''').createSource();
+    _context = AnalysisContextFactory.oldContextWithCore();
+    _context.analysisOptions = new AnalysisOptionsImpl()..incremental = true;
+    _context.applyChanges(new ChangeSet()..addedSource(source));
+    // remember compilation unit
+    _analyzeAll_assertFinished();
+    CompilationUnit unit = _context.getResolvedCompilationUnit2(source, source);
+    // add overlay
+    _context.setContents(source, r'''
+main() {
+  print(12);
+}
+''');
+    _analyzeAll_assertFinished();
+    expect(_context.getResolvedCompilationUnit2(source, source), unit);
+    // remove overlay
+    _context.setContents(source, null);
+    _analyzeAll_assertFinished();
+    expect(_context.getResolvedCompilationUnit2(source, source), unit);
+  }
+
   Future test_applyChanges_removeContainer() {
     _context = AnalysisContextFactory.oldContextWithCore();
     SourcesChangedListener listener = new SourcesChangedListener();
     _context.onSourcesChanged.listen(listener.onData);
     _sourceFactory = _context.sourceFactory;
     String libAContents = r'''
 library libA;
 import 'libB.dart';''';
     Source libA = _addSource("/libA.dart", libAContents);
     String libBContents = "library libB;";
@@ skipping 6168 matching lines @@
   @override
   bool exists() => true;
 }
 
 class _UniversalCachePartitionTest_test_setMaxCacheSize
     implements CacheRetentionPolicy {
   @override
   RetentionPriority getAstPriority(Source source, SourceEntry sourceEntry) =>
       RetentionPriority.LOW;
 }