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)

constructor() {
      this._capability = createPromiseCapability();
      this._transport = null;
      this._worker = null;
      /**
       * Unique identifier for the document loading task.
       * @type {string}
       */
      this.docId = "d" + nextDocumentId++;
      /**
       * Whether the loading task is destroyed or not.
       * @type {boolean}
       */
      this.destroyed = false;
      /**
       * Callback to request a password if a wrong or no password was provided.
       * The callback receives two parameters: a function that should be called
       * with the new password, and a reason (see {@link PasswordResponses}).