One more fix for making removing overlays incremental changes.

pkg/analysis_server/test/analysis/update_content_test.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 test.analysis.updateContent;
 
+import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/constants.dart';
 import 'package:analysis_server/src/protocol.dart';
 import 'package:analysis_server/src/services/index/index.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 import 'package:typed_mock/typed_mock.dart';
 import 'package:unittest/unittest.dart';
@@ skipping 153 matching lines @@
       expect(sources, hasLength(1));
       expect(sources[0].fullName, filePath);
     }
     expect(_getUserSources(context2), isEmpty);
     // remove the overlay - no sources
     server.updateContent('2', {filePath: new RemoveContentOverlay()});
     expect(_getUserSources(context1), isEmpty);
     expect(_getUserSources(context2), isEmpty);
   }
 
+  test_removeOverlay_incrementalChange() async {
+    createProject();
+    addTestFile('main() { print(1); }');
+    await server.onAnalysisComplete;
+    CompilationUnit unit = _getTestUnit();
+    // add an overlay
+    server.updateContent(
+        '1', {testFile: new AddContentOverlay('main() { print(2); }')});
+    // it was an incremental change
+    await server.onAnalysisComplete;
+    expect(_getTestUnit(), same(unit));
+    // remove overlay
+    server.updateContent('2', {testFile: new RemoveContentOverlay()});
+    // it was an incremental change
+    await server.onAnalysisComplete;
+    expect(_getTestUnit(), same(unit));
+  }
+
   test_sendNoticesAfterNopChange() async {
     createProject();
     addTestFile('');
     await server.onAnalysisComplete;
     // add an overlay
     server.updateContent(
         '1', {testFile: new AddContentOverlay('main() {} main() {}')});
     await server.onAnalysisComplete;
     // clear errors and make a no-op change
     filesErrors.clear();
@@ skipping 17 matching lines @@
     filesErrors.clear();
     server.test_flushAstStructures(testFile);
     server.updateContent('2', {
       testFile: new ChangeContentOverlay([new SourceEdit(0, 4, 'main')])
     });
     await server.onAnalysisComplete;
     // errors should have been resent
     expect(filesErrors, isNotEmpty);
   }
 
+  CompilationUnit _getTestUnit() {
+    ContextSourcePair pair = server.getContextSourcePair(testFile);
+    AnalysisContext context = pair.context;
+    Source source = pair.source;
+    return context.getResolvedCompilationUnit2(source, source);
+  }
+
   List<Source> _getUserSources(AnalysisContext context) {
     List<Source> sources = <Source>[];
     context.sources.forEach((source) {
       if (source.fullName.startsWith('/User/')) {
         sources.add(source);
       }
     });
     return sources;
   }
 }
 
 class _ArgumentMatcher_CompilationUnit extends ArgumentMatcher {
   final String file;
 
   _ArgumentMatcher_CompilationUnit(this.file);
 
   @override
   bool matches(arg) {
     return arg is CompilationUnit && arg.element.source.fullName == file;
   }
 }
 
 class _MockIndex extends TypedMock implements Index {
   noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
 }