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)

*   A promise that is resolved with an {@link OptionalContentConfig} instance.
 *   The default value is `null`.
 * @property {PDFRenderingQueue} renderingQueue - The rendering queue object.
 * @property {IPDFTextLayerFactory} textLayerFactory
 * @property {number} [textLayerMode] - Controls if the text layer used for
 *   selection and searching is created, and if the improved text selection
 *   behaviour is enabled. The constants from {TextLayerMode} should be used.
 *   The default value is `TextLayerMode.ENABLE`.
 * @property {IPDFAnnotationLayerFactory} annotationLayerFactory
 * @property {IPDFXfaLayerFactory} xfaLayerFactory
 * @property {IPDFStructTreeLayerFactory} structTreeLayerFactory
 * @property {string} [imageResourcesPath] - Path for image resources, mainly
 *   for annotation icons. Include trailing slash.
 * @property {boolean} renderInteractiveForms - Turns on rendering of
 *   interactive form elements. The default value is `true`.
 * @property {string} renderer - 'canvas' or 'svg'. The default is 'canvas'.
 * @property {boolean} [enableWebGL] - Enables WebGL accelerated rendering for
 *   some operations. The default value is `false`.
 * @property {boolean} [useOnlyCssZoom] - Enables CSS only zooming. The default
 *   value is `false`.
 * @property {number} [maxCanvasPixels] - The maximum supported canvas size in
 *   total pixels, i.e. width * height. Use -1 for no limit. The default value
 *   is 4096 * 4096 (16 mega-pixels).
 * @property {IL10n} l10n - Localization service.
 */
const MAX_CANVAS_PIXELS = viewerCompatibilityParams.maxCanvasPixels || 16777216;
/**
 * @implements {IRenderableView}
 */
class PDFPageView {