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

pkg/analysis_server/lib/src/status/get_handler.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library analysis_server.src.status.get_handler;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:convert';
 import 'dart:io';
@@ skipping 1689 matching lines @@
         buffer.write(makeLink(CONTEXT_DIAGNOSTICS_PATH,
             {CONTEXT_QUERY_PARAM: folder.path}, 'diagnostics'));
         buffer.write(']</b></small>');
         if (!folder.getChild('.packages').exists) {
           buffer.write(' <small>[no .packages file]</small>');
         }
       });
       // TODO(brianwilkerson) Add items for the SDK contexts (currently only one).
       buffer.write('</p>');
 
-      int freq = AnalysisServer.performOperationDelayFreqency;
+      int freq = AnalysisServer.performOperationDelayFrequency;
       String delay = freq > 0 ? '1 ms every $freq ms' : 'off';
 
       buffer.write('<p><b>Performance Data</b></p>');
       buffer.write('<p>Perform operation delay: $delay</p>');
       buffer.write('<p>');
       buffer.write(makeLink(ANALYSIS_PERFORMANCE_PATH, {}, 'Task data'));
       buffer.write('</p>');
     }, (StringBuffer buffer) {
       _writeSubscriptionMap(
           buffer, AnalysisService.VALUES, analysisServer.analysisServices);
@@ skipping 762 matching lines @@
    */
   static String makeLink(
       String path, Map<String, String> params, String innerHtml,
       [bool hasError = false]) {
     Uri uri = new Uri(path: path, queryParameters: params);
     String href = HTML_ESCAPE.convert(uri.toString());
     String classAttribute = hasError ? ' class="error"' : '';
     return '<a href="$href"$classAttribute>$innerHtml</a>';
   }
 }