Make NavigationOperation a MergeableOperation.

pkg/analysis_server/lib/src/operation/operation_analysis.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 operation.analysis;
 
 import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/computer/computer_highlights.dart';
 import 'package:analysis_server/src/computer/computer_highlights2.dart';
 import 'package:analysis_server/src/computer/computer_occurrences.dart';
@@ skipping 211 matching lines @@
 void _sendNotification(AnalysisServer server, f()) {
   ServerPerformanceStatistics.notices.makeCurrentWhile(() {
     try {
       f();
     } catch (exception, stackTrace) {
       server.sendServerErrorNotification(exception, stackTrace);
     }
   });
 }
 
-class NavigationOperation extends _NotificationOperation {
+class NavigationOperation extends _NotificationOperation
+    implements MergeableOperation {
   NavigationOperation(AnalysisContext context, Source source)
       : super(context, source);
 
   @override
   void perform(AnalysisServer server) {
     sendAnalysisNotificationNavigation(server, context, source);
   }
+
+  @override
+  bool merge(ServerOperation other) {
+    return other is NavigationOperation &&
+        other.context == context &&
+        other.source == source;
+  }
 }
 
 /**
  * Instances of [PerformAnalysisOperation] perform a single analysis task.
  */
 class PerformAnalysisOperation extends ServerOperation {
   static const int IDLE_CACHE_SIZE = AnalysisOptionsImpl.DEFAULT_CACHE_SIZE;
   static const int WORKING_CACHE_SIZE = 512;
 
   final bool isContinue;
@@ skipping 243 matching lines @@
 abstract class _SingleFileOperation extends SourceSensitiveOperation {
   final String file;
 
   _SingleFileOperation(AnalysisContext context, this.file) : super(context);
 
   @override
   bool shouldBeDiscardedOnSourceChange(Source source) {
     return source.fullName == file;
   }
 }