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)

}
  if (!PDFViewerApplication.supportsPrinting) {
    appConfig.toolbar.print.classList.add("hidden");
    appConfig.secondaryToolbar.printButton.classList.add("hidden");
  }
  if (!PDFViewerApplication.supportsFullscreen) {
    appConfig.toolbar.presentationModeButton.classList.add("hidden");
    appConfig.secondaryToolbar.presentationModeButton.classList.add("hidden");
  }
  if (PDFViewerApplication.supportsIntegratedFind) {
    appConfig.toolbar.viewFind.classList.add("hidden");
  }
  appConfig.mainContainer.addEventListener(
    "transitionend",
    function (evt) {
      if (evt.target ===  this) {
        PDFViewerApplication.eventBus.dispatch("resize", { source: this });
      }
    },
    true
  );
  try {
    webViewerOpenFileViaURL(file);
  } catch (reason) {
    PDFViewerApplication.l10n.get("loading_error").then(msg => {
      PDFViewerApplication._documentError(msg, reason);
    });
  }
}
function webViewerOpenFileViaURL(file) {