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(messageHandler, loadingTask, networkStream, params) {
    this.messageHandler = messageHandler;
    this.loadingTask = loadingTask;
    this.commonObjs = new PDFObjects();
    this.fontLoader = new FontLoader({
      docId: loadingTask.docId,
      onUnsupportedFeature: this._onUnsupportedFeature.bind(this),
      ownerDocument: params.ownerDocument,
    });
    this._params = params;
    this.CMapReaderFactory = new params.CMapReaderFactory({
      baseUrl: params.cMapUrl,
      isCompressed: params.cMapPacked,
    });
    this.destroyed = false;
    this.destroyCapability = null;
    this._passwordCapability = null;
    this._networkStream = networkStream;
    this._fullReader = null;
    this._lastProgress = null;
    this.pageCache = [];
    this.pagePromises = [];
    this.downloadInfoCapability = createPromiseCapability();
    this.setupMessageHandler();
  }
  get annotationStorage() {