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)

errorWrapper.hidden = false;
      const errorMessage = errorWrapperConfig.errorMessage;
      errorMessage.textContent = message;
      const closeButton = errorWrapperConfig.closeButton;
      closeButton.onclick = function () {
        errorWrapper.hidden = true;
      };
      const errorMoreInfo = errorWrapperConfig.errorMoreInfo;
      const moreInfoButton = errorWrapperConfig.moreInfoButton;
      const lessInfoButton = errorWrapperConfig.lessInfoButton;
      moreInfoButton.onclick = function () {
        errorMoreInfo.hidden = false;
        moreInfoButton.hidden = true;
        lessInfoButton.hidden = false;
        errorMoreInfo.style.height = errorMoreInfo.scrollHeight + "px";
      };
      lessInfoButton.onclick = function () {
        errorMoreInfo.hidden = true;
        moreInfoButton.hidden = false;
        lessInfoButton.hidden = true;
      };
      moreInfoButton.oncontextmenu = noContextMenuHandler;
      lessInfoButton.oncontextmenu = noContextMenuHandler;
      closeButton.oncontextmenu = noContextMenuHandler;
      moreInfoButton.hidden = false;
      lessInfoButton.hidden = true;
      Promise.all(moreInfoText).then(parts => {
        errorMoreInfo.value = parts.join("\n");
      });
    } else {