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)

const task = new PDFDocumentLoadingTask();
  let source;
  if (typeof src === "string" || src instanceof URL) {
    source = { url: src };
  } else if (isArrayBuffer(src)) {
    source = { data: src };
  } else if (src instanceof PDFDataRangeTransport) {
    source = { range: src };
  } else {
    if (typeof src !== "object") {
      throw new Error(
        "Invalid parameter in getDocument, " +
          "need either string, URL, Uint8Array, or parameter object."
      );
    }
    if (!src.url && !src.data && !src.range) {
      throw new Error(
        "Invalid parameter object: need either .data, .range or .url"
      );
    }
    source = src;
  }
  const params = Object.create(null);
  let rangeTransport = null,
    worker = null;
  for (const key in source) {
    const value = source[key];
    switch (key) {
      case "url":
        if (typeof window !== "undefined") {