anchor.diff:  import 'package:analyzer/src/generated/incremental_resolution_validator.dart';
   import 'package:analyzer/src/services/lint.dart';
   import 'package:analyzer/src/task/task_dart.dart';
  -import 'package:analyzer/src/util/lru_map.dart';
   
   import '../../instrumentation/instrumentation.dart';
   import 'ast.dart';
  
positive.code:       return;
      }
      // Check if the content of the source is the same as it was the last time.
      String sourceContent = _prevOverlayCache.get(source);
      if (sourceContent != null) {
        try {
          TimestampedData<String> fileContents = getContents(source);
          if (fileContents.data == sourceContent) {
  
negative.code:    * A cache of content used to override the default content of a source.
     */
    ContentCache _contentCache = new ContentCache();
  
    /**
     * The source factory used to create the sources that can be analyzed in this context.
  