anchor.diff:    // Update current results
     return results;
   };
  -
  -/// [GetContentsFailedMapper] processes session log messages
  -/// and extracts severe log messages starting with
  -/// 'Internal error while performing the task: get contents of '.
  -///
  -/// Results keys are [sdkVersion] and values are a list containing
  -///
  -/// * [sessionId]
  -/// * failure time (ms since epoch)
  -/// * failure type (GET_CONTENTS_FAILED)
  -/// * uri
  -///
  -class GetContentsFailedMapper extends _AbstractFailureMapper {
  -  @override
  -  void mapLogMessage(int time, String msgType, String logMessageText) {
  -    if (msgType == 'Log') {
  -      if (logMessageText.startsWith('SEVERE:')) {
  -        _processSevereLogMsg(time, logMessageText);
  -      }
  -    }
  -  }
  -
  -  /// Extract exceptions and failures from SEVERE log messages
  -  void _processSevereLogMsg(int time, String logMessageText) {
  -    var start = logMessageText.indexOf(':', 7);
  -    var msgText = logMessageText.substring(start + 1).replaceAll('::', ':');
  -
  -    // Record getContent failed messages
  -    if (msgText.startsWith(GET_CONTENTS_FAILED_PREFIX)) {
  -      var uri = msgText.substring(GET_CONTENTS_FAILED_PREFIX.length);
  -      _recordFailure(time, GET_CONTENTS_FAILED, uri);
  -      return;
  -    }
  -  }
  -}
   
   /// [SevereLogMapper] processes session log messages
   /// and extracts severe log messages that do NOT start with
  
positive.code:   void _processSevereLogMsg(int time, String logMessageText) {
      var start = logMessageText.indexOf(':', 7);
      var msgText = logMessageText.substring(start + 1).replaceAll('::', ':');
  
      // Record all except getContent failed messages
      if (!msgText.startsWith(GET_CONTENTS_FAILED_PREFIX)) {
        _recordFailure(time, SEVERE_LOG, msgText);
        return;
      }
    }
  }
  
  abstract class _AbstractFailureMapper extends InstrumentationMapper {
    void _recordFailure(int time, String resultType, [resultData]) {
      addResult(sdkVersion, [sessionId, time, resultType, resultData]);
    }
  }
  
negative.code: 
  import 'package:sintr_worker_lib/instrumentation_query.dart';
  
  const SEVERE_LOG = 'SevereLog';
  
  /// Add an extraction result to the overall [results]
  