Partially revert notification of package map computation

pkg/analysis_server/lib/src/analysis_server.dart

Index: pkg/analysis_server/lib/src/analysis_server.dart
diff --git a/pkg/analysis_server/lib/src/analysis_server.dart b/pkg/analysis_server/lib/src/analysis_server.dart
index cb66929cd6f14b9e61dcc1ec00503244ca61fd01..f8e2026e59d4b8737588dfe99efc565f9b50ab8c 100644
--- a/pkg/analysis_server/lib/src/analysis_server.dart
+++ b/pkg/analysis_server/lib/src/analysis_server.dart
@@ -332,7 +332,6 @@ class AnalysisServer {
     ServerContextManagerCallbacks contextManagerCallbacks =
         new ServerContextManagerCallbacks(this, resourceProvider);
     contextManager.callbacks = contextManagerCallbacks;
-    contextManager.onComputingPackageMap.listen(_computingPackageMap);
     _noErrorNotification = options.noErrorNotification;
     AnalysisEngine.instance.logger = new AnalysisLogger(this);
     _onAnalysisStartedController = new StreamController.broadcast();
@@ -1525,6 +1524,10 @@ class ServerContextManagerCallbacks extends ContextManagerCallbacks {
   }
 
   @override
+  void computingPackageMap(bool computing) =>
+      analysisServer._computingPackageMap(computing);
+
+  @override
   void removeContext(Folder folder, List<String> flushedFiles) {
     AnalysisContext context = analysisServer.folderMap.remove(folder);
     sendAnalysisNotificationFlushResults(analysisServer, flushedFiles);