anchor.diff:  import 'sharing/gists.dart';
   import 'sharing/mutable_gist.dart';
   import 'src/ga.dart';
  -import 'src/summarize.dart';
   import 'src/util.dart';
   
   Playground get playground => _playground;
  
positive.code:           "https://gist.github.com/anonymous/${newGist.id}", '_blank'));
        GistToInternalIdMapping mapping = new GistToInternalIdMapping()
          ..gistId = newGist.id
          ..internalId=_mappingId;
        dartSupportServices.storeGist(mapping);
      }).catchError((e) {
        String message = 'Error saving gist: ${e}';
  
negative.code:     }
    }
  
    Future<String> _createSummary() {
      return dartSupportServices.getUnusedMappingId().then((UuidContainer id) {
        _mappingId = id.uuid;
        SourcesRequest input = new SourcesRequest()
          ..sources = {'dart':_context.dartSource, 'css': _context.cssSource, 'html': _context.htmlSource};
        return dartServices.summarize(input);
      }).then((SummaryText summary) {
        return '${summary.text}\n Find this at [dartpad.dartlang.org/?source=${_mappingId}](https://dartpad.dartlang.org/?source=${_mappingId}).';
      }).catchError((e) {
        _logger.severe(e);
      });
    }
  
    /// Perform static analysis of the source code. Return whether the code
  