anchor.diff:                 await _handleTask(task);
                  log.perf("Task $task completed", sw.elapsedMilliseconds);
               }
  -
         });
   }
   
   _handleTask(tasks.Task task) async {
     log.trace("Starting task $task");
  -  String lastSeenMd5 = null;
  -  String cachedSource = null;
   
     Stopwatch sw = new Stopwatch()..start();
     try {
  
positive.code: 
      gae_utils.CloudStorageLocation sourceLocation = await task.sourceLocation;
      if (lastSeenMd5 != null && sourceLocation.md5 == lastSeenMd5) {
        log.trace("Source cache hit: $lastSeenMd5");
        if (cachedSource == null) {
          throw "Invariant check failed: Cached key matched but source was null";
        }
  
        sourceJSON = cachedSource;
      } else {
        sourceJSON = await
          gae_utils.CloudStorage.getFileContentsByLocation(sourceLocation)
              .transform(UTF8.decoder).join();
          lastSeenMd5 = sourceLocation.md5;
          cachedSource = sourceJSON;
          log.trace("Cache miss: Source acquired $lastSeenMd5");
      }
  
      var sourceMap = JSON.decode(sourceJSON);
  
negative.code: 
                 if (task == null) {
                   log.info("Got null next ready task, sleeping");
                   await new Future.delayed(DELAY_BETWEEN_TASK_POLLS);
                   continue;
                 }
  
  