Attach (recommended) or Link to PDF file here:
[multiple.pdf](https://github.com/mozilla/pdf.js/files/6344777/multiple.pdf)

Steps to reproduce the problem:
1. Write something in a field

What is the expected behavior? (add screenshot)
The 3 fields must have the same value

What went wrong? (add screenshot)
The 2 other fields are empty

The three fields share the same name `Text3`.
It works as expected in Adobe and Chrome.
selectElement.multiple = true;
          },
          remove() {
            const options = selectElement.options;
            const index = detail.remove;
            options[index].selected = false;
            selectElement.remove(index);
            if (options.length > 0) {
              const i = Array.prototype.findIndex.call(
                options,
                option => option.selected
              );
              if (i === -1) {
                options[0].selected = true;
              }
            }
            storage.setValue(id, {
              value: getValue(event,  true),
              items: getItems(event),
            });
          },
          clear() {