Listen for context add/remove and unit invalidation to update the index.

pkg/analysis_server/lib/src/server/driver.dart

Index: pkg/analysis_server/lib/src/server/driver.dart
diff --git a/pkg/analysis_server/lib/src/server/driver.dart b/pkg/analysis_server/lib/src/server/driver.dart
index 4f9e4720a8bf01dff66709b77bcd9ea160471179..7db68b655d58f914a9405729342ace8d20036feb 100644
--- a/pkg/analysis_server/lib/src/server/driver.dart
+++ b/pkg/analysis_server/lib/src/server/driver.dart
@@ -343,7 +343,7 @@ class Driver implements ServerStarter {
     // TODO (danrubel) Remove this workaround
     // once the underlying VM and dart:io issue has been fixed.
     if (results[INTERNAL_DELAY_FREQUENCY] != null) {
-      AnalysisServer.performOperationDelayFreqency =
+      AnalysisServer.performOperationDelayFrequency =
           int.parse(results[INTERNAL_DELAY_FREQUENCY], onError: (_) => 0);
     }