he textarea should not have dataTransfer on input event with
  // insertFromPaste type.
  textarea.addEventListener("input", (e) => {
    assert_equals(e.inputType, "insertFromPaste");
    assert_equals(e.dataTransfer, null);
    assert_equals(e.data, "copyMe");
  });
  promise_test(async () => {
    const range = document.createRange();
    const contentToCopy = document.getElementById("copy");
    range.selectNodeContents(contentToCopy);
    const selection = window.getSelection();
    selection.removeAll