analyzer: Make new filesWithClientDiagnostics field private

Change-Id: I5ff762c54434fb81425275ef002b4186ceedc1dd
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/341801
Reviewed-by: Phil Quitslund <pquitslund@google.com>
Commit-Queue: Phil Quitslund <pquitslund@google.com>
Auto-Submit: Samuel Rawlins <srawlins@google.com>
diff --git a/pkg/analysis_server/lib/src/lsp/lsp_analysis_server.dart b/pkg/analysis_server/lib/src/lsp/lsp_analysis_server.dart
index cb97077..8dcd723 100644
--- a/pkg/analysis_server/lib/src/lsp/lsp_analysis_server.dart
+++ b/pkg/analysis_server/lib/src/lsp/lsp_analysis_server.dart
@@ -135,7 +135,7 @@
   /// This is an optimization to avoid sending empty diagnostics when they are
   /// unnecessary (at startup, when a file is re-analyzed because a file it
   /// imports was modified, etc).
-  final Set<String> filesWithClientDiagnostics = {};
+  final Set<String> _filesWithClientDiagnostics = {};
 
   /// Initialize a newly created server to send and receive messages to the
   /// given [channel].
@@ -632,15 +632,15 @@
   }
 
   void publishDiagnostics(String path, List<Diagnostic> errors) {
-    if (errors.isEmpty && !filesWithClientDiagnostics.contains(path)) {
+    if (errors.isEmpty && !_filesWithClientDiagnostics.contains(path)) {
       // Don't sent empty set if client is already empty.
       return;
     }
 
     if (errors.isEmpty) {
-      filesWithClientDiagnostics.remove(path);
+      _filesWithClientDiagnostics.remove(path);
     } else {
-      filesWithClientDiagnostics.add(path);
+      _filesWithClientDiagnostics.add(path);
     }
 
     final params = PublishDiagnosticsParams(