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.
return this._initializedCapability.settled;
  },
  get initializedPromise() {
    return this._initializedCapability.promise;
  },
  zoomIn(ticks) {
    if (this.pdfViewer.isInPresentationMode) {
      return;
    }
    let newScale = this.pdfViewer.currentScale;
    do {
      newScale = (newScale * DEFAULT_SCALE_DELTA).toFixed(2);
      newScale = Math.ceil(newScale * 10) / 10;
      newScale = Math.min(MAX_SCALE, newScale);
    } while (--ticks > 0 && newScale < MAX_SCALE);
    this.pdfViewer.currentScaleValue = newScale;
  },
  zoomOut(ticks) {
    if (this.pdfViewer.isInPresentationMode) {
      return;
    }
    let newScale = this.pdfViewer.currentScale;
    do {
      newScale = (newScale / DEFAULT_SCALE_DELTA).toFixed(2);
      newScale = Math.floor(newScale * 10) / 10;
      newScale = Math.max(MIN_SCALE, newScale);
    } while (--ticks > 0 && newScale > MIN_SCALE);
    this.pdfViewer.currentScaleValue = newScale;
  },
  zoomReset() {