Add ApplyChangesStatus to AnalysisContext.applyChanges() and use it in DAS.

pkg/analysis_server/test/analysis_server_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.analysis_server;
 
 import 'dart:async';
 
 import 'package:analysis_server/plugin/protocol/protocol.dart';
 import 'package:analysis_server/src/analysis_server.dart';
@@ skipping 466 matching lines @@
 
   Future test_unknownRequest() {
     server.handlers = [new EchoHandler()];
     var request = new Request('my22', 'randomRequest');
     return channel.sendRequest(request).then((Response response) {
       expect(response.id, equals('my22'));
       expect(response.error, isNotNull);
     });
   }
 
+  test_watch_modifyFile_hasOverlay() async {
+    server.serverServices.add(ServerService.STATUS);
+    // configure the project
+    String projectPath = '/root';
+    String filePath = '/root/test.dart';
+    resourceProvider.newFolder(projectPath);
+    resourceProvider.newFile(filePath, '// 111');
+    server.setAnalysisRoots('0', ['/root'], [], {});
+    await pumpEventQueue();
+    // add overlay
+    server.updateContent('1', {filePath: new AddContentOverlay('// 222')});
+    await pumpEventQueue();
+    // update the file
+    channel.notificationsReceived.clear();
+    resourceProvider.modifyFile(filePath, '// 333');
+    await pumpEventQueue();
+    // the file has an overlay, so the file-system change was ignored
+    expect(channel.notificationsReceived.any((notification) {
+      return notification.event == SERVER_STATUS;
+    }), isFalse);
+  }
+
   void _configureSourceFactory(AnalysisContext context) {
     var resourceUriResolver = new ResourceUriResolver(resourceProvider);
     var packageUriResolver = new PackageMapUriResolver(
         resourceProvider, packageMapProvider.packageMap);
     context.sourceFactory =
         new SourceFactory([packageUriResolver, resourceUriResolver]);
   }
 }
 
 class EchoHandler implements RequestHandler {
@@ skipping 17 matching lines @@
   _MockServerOperation(this.context);
 
   @override
   ServerOperationPriority get priority => ServerOperationPriority.ANALYSIS;
 
   @override
   void perform(AnalysisServer server) {
     isComplete = true;
   }
 }