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)

PDFViewerApplication.requestPresentationMode();
}
function webViewerPrint() {
  PDFViewerApplication.triggerPrinting();
}
function webViewerDownload() {
  PDFViewerApplication.downloadOrSave({ sourceEventType: "download" });
}
function webViewerSave() {
  PDFViewerApplication.downloadOrSave({ sourceEventType: "save" });
}
function webViewerFirstPage() {
  if (PDFViewerApplication.pdfDocument) {
    PDFViewerApplication.page = 1;
  }
}
function webViewerLastPage() {
  if (PDFViewerApplication.pdfDocument) {
    PDFViewerApplication.page = PDFViewerApplication.pagesCount;
  }
}
function webViewerNextPage() {
  PDFViewerApplication.pdfViewer.nextPage();
}
function webViewerPreviousPage() {
  PDFViewerApplication.pdfViewer.previousPage();
}
function webViewerZoomIn() {