anchor.diff:  
   // TODO: Implement memory based limiting, once `approximateByteCount` is exposed in engine
   class PictureCache {
  -  final Map<Object, PictureStreamCompleter> _cache = <Object, PictureStreamCompleter>{};
  +  final Map<Object, PictureStreamCompleter> _cache =
  +      <Object, PictureStreamCompleter>{};
   
     /// Maximum number of entries to store in the cache.
     ///
  
positive.code:   set maximumSize(int value) {
      assert(value != null);
      assert(value >= 0);
      if (value == maximumSize)
        return;
      _maximumSize = value;
      if (maximumSize == 0) {
        _cache.clear();
      } else {
        while (_cache.length > maximumSize)
          _cache.remove(_cache.keys.first);
      }
    }
  
  
negative.code:   /// key is moved to the "most recently used" position.
    ///
    /// The arguments must not be null. The `loader` cannot return null.
    PictureStreamCompleter putIfAbsent(
        Object key, PictureStreamCompleter loader()) {
      assert(key != null);
      assert(loader != null);
      PictureStreamCompleter result = _cache[key];
  