Get rid of ContextManager._contexts.

pkg/analysis_server/lib/src/analysis_server.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;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:core' hide Resource;
 import 'dart:math' show max;
@@ skipping 1222 matching lines @@
     });
     //
     // Update the defaults used to create new contexts.
     //
     optionUpdaters.forEach((OptionUpdater optionUpdater) {
       optionUpdater(defaultContextOptions);
     });
   }
 
   /**
-   * Return a set of contexts containing all of the resources in the given list
-   * of [resources].
+   * Return a set of all contexts whose associated folder is contained within,
+   * or equal to, one of the resources in the given list of [resources].
    */
   Set<AnalysisContext> _getContexts(List<Resource> resources) {
     Set<AnalysisContext> contexts = new HashSet<AnalysisContext>();
     resources.forEach((Resource resource) {
       if (resource is Folder) {
         contexts.addAll(contextManager.contextsInAnalysisRoot(resource));
       }
     });
     return contexts;
   }
@@ skipping 309 matching lines @@
   /**
    * The [PerformanceTag] for time spent in server request handlers.
    */
   static PerformanceTag serverRequests = new PerformanceTag('serverRequests');
 
   /**
    * The [PerformanceTag] for time spent in split store microtasks.
    */
   static PerformanceTag splitStore = new PerformanceTag('splitStore');
 }