STR:
  - Go to https://mozilla.github.io/pdf.js/web/viewer.html
  - Click on "Open File" and open a pdf

The `Download` button and the `Current view` one just disappear.
I can reproduce this bug with Firefox nightly, Chrome stable and Epiphany on debian.
if (
      (this._wheelUnusedTicks > 0 && ticks < 0) ||
      (this._wheelUnusedTicks < 0 && ticks > 0)
    ) {
      this._wheelUnusedTicks = 0;
    }
    this._wheelUnusedTicks += ticks;
    const wholeTicks =
      Math.sign(this._wheelUnusedTicks) *
      Math.floor(Math.abs(this._wheelUnusedTicks));
    this._wheelUnusedTicks -= wholeTicks;
    return wholeTicks;
  },
  /**
   * Should be called *after* all pages have loaded, or if an error occurred,
   * to unblock the "load" event; see https://bugzilla.mozilla.org/show_bug.cgi?id=1618553
   * @private
   */
  _unblockDocumentLoadEvent() {