Support for overlay only files in Analysis Server with the new driver.

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 283e662eb4004170ac41211bb8d2641feedc069f..7751fb63ddd1401d7be1fcc6d190d00dc659c3ee 100644
--- a/pkg/analysis_server/lib/src/analysis_server.dart
+++ b/pkg/analysis_server/lib/src/analysis_server.dart
@@ -1487,6 +1487,11 @@ class AnalysisServer {
         driverMap.values.forEach((driver) {
           driver.changeFile(file);
         });
+
+        // If the file did not exist, and is "overlay only", it still should be
+        // analyzed. Add it to driver to which it should have been added.
+        contextManager.getDriverFor(file)?.addFile(file);
+
         // TODO(scheglov) implement other cases
       });
       return;