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)

this.textLayerFactory = options.textLayerFactory;
    this.annotationLayerFactory = options.annotationLayerFactory;
    this.xfaLayerFactory = options.xfaLayerFactory;
    this.structTreeLayerFactory = options.structTreeLayerFactory;
    this.renderer = options.renderer || RendererType.CANVAS;
    this.enableWebGL = options.enableWebGL || false;
    this.l10n = options.l10n || NullL10n;
    this.paintTask = null;
    this.paintedViewportMap = new WeakMap();
    this.renderingState = RenderingStates.INITIAL;
    this.resume = null;
    this._renderError = null;
    this.annotationLayer = null;
    this.textLayer = null;
    this.zoomLayer = null;
    this.xfaLayer = null;
    this.structTreeLayer = null;
    const div = document.createElement("div");
    div.className = "page";
    div.style.width = Math.floor(this.viewport.width) + "px";
    div.style.height = Math.floor(this.viewport.height) + "px";
    div.setAttribute("data-page-number", this.id);
    div.setAttribute("role", "region");
    this.l10n.get("page_landmark", { page: this.id }).then(msg => {
      div.setAttribute("aria-label", msg);
    });
    this.div = div;
    container.appendChild(div);
  }
  setPdfPage(pdfPage) {