I was wondering if WebGL is considered stable enough to be enabled by default. It makes some PDFs render much faster and it has been off by default for a while now, so we have had quite some time to test it.

If we decide to enable WebGL by default, we should not forget to update https://github.com/mozilla/pdf.js/blob/master/extensions/chromium/preferences_schema.json#L39 as well.

/cc @yurydelendik 
/cc @Snuffleupagus (because IIRC you were testing WebGL too)

let turnPage = 0,
      turnOnlyIfPageFit = false;
    switch (evt.keyCode) {
      case 38: 
      case 33: 
        
        if (pdfViewer.isVerticalScrollbarEnabled) {
          turnOnlyIfPageFit = true;
        }
        turnPage = -1;
        break;
      case 8: 
        if (!isViewerInPresentationMode) {
          turnOnlyIfPageFit = true;
        }
        turnPage = -1;
        break;
      case 37: 
        
        if (pdfViewer.isHorizontalScrollbarEnabled) {
          turnOnlyIfPageFit = true;
        }
      
      case 75: 
      case 80: 
        turnPage = -1;
        break;
      case 27: 
        if (PDFViewerApplication.secondaryToolbar.isOpen) {
          PDFViewerApplication.secondaryToolbar.close();