anchor.diff:  /// {@category Interface}
   /// {@category winrt}
   class IFileOpenPicker extends IInspectable {
  +  final Allocator allocator;
  +
     // vtable begins at 6, is 11 entries long.
  -  IFileOpenPicker(Pointer<COMObject> ptr) : super(ptr);
  +  IFileOpenPicker(Pointer<COMObject> ptr, {this.allocator = calloc})
  +      : super(ptr);
   
     int get ViewMode {
       final retValuePtr = calloc<Int32>();
  
positive.code:   }
  
    IVector<String> get FileTypeFilter {
      final retValuePtr = calloc<COMObject>();
  
      final hr = ptr.ref.lpVtbl.value
          .elementAt(14)
  
negative.code: 
      if (FAILED(hr)) throw WindowsException(hr);
  
      return IVector(retValuePtr, allocator: allocator);
    }
  
    Pointer<COMObject> PickSingleFileAsync() {
  