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 (!rangeReader) {
        sink.close();
        return;
      }
      sink.onPull = () => {
        rangeReader
          .read()
          .then(function ({ value, done }) {
            if (done) {
              sink.close();
              return;
            }
            assert(
              isArrayBuffer(value),
              "GetRangeReader - expected an ArrayBuffer."
            );
            sink.enqueue(new Uint8Array(value), 1, [value]);
          })
          .catch(reason => {
            sink.error(reason);
          });
      };
      sink.onCancel = reason => {
        rangeReader.cancel(reason);
        sink.ready.catch(readyReason => {
          if (this.destroyed) {