Make NavigationOperation a MergeableOperation.

pkg/analysis_server/lib/src/operation/operation_analysis.dart

Index: pkg/analysis_server/lib/src/operation/operation_analysis.dart
diff --git a/pkg/analysis_server/lib/src/operation/operation_analysis.dart b/pkg/analysis_server/lib/src/operation/operation_analysis.dart
index e7ba700b93b8f56cdf9428eb9a6fd90191b10ee0..4d1e60e8ad1e30d7fa2cda17f0c62ad254589409 100644
--- a/pkg/analysis_server/lib/src/operation/operation_analysis.dart
+++ b/pkg/analysis_server/lib/src/operation/operation_analysis.dart
@@ -229,7 +229,8 @@ void _sendNotification(AnalysisServer server, f()) {
   });
 }
 
-class NavigationOperation extends _NotificationOperation {
+class NavigationOperation extends _NotificationOperation
+    implements MergeableOperation {
   NavigationOperation(AnalysisContext context, Source source)
       : super(context, source);
 
@@ -237,6 +238,13 @@ class NavigationOperation extends _NotificationOperation {
   void perform(AnalysisServer server) {
     sendAnalysisNotificationNavigation(server, context, source);
   }
+
+  @override
+  bool merge(ServerOperation other) {
+    return other is NavigationOperation &&
+        other.context == context &&
+        other.source == source;
+  }
 }
 
 /**