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.pendingCleanup = false;
    if (!optionalContentConfigPromise) {
      optionalContentConfigPromise = this._transport.getOptionalContentConfig();
    }
    let intentState = this._intentStates.get(renderingIntent);
    if (!intentState) {
      intentState = Object.create(null);
      this._intentStates.set(renderingIntent, intentState);
    }
    
    if (intentState.streamReaderCancelTimeout) {
      clearTimeout(intentState.streamReaderCancelTimeout);
      intentState.streamReaderCancelTimeout = null;
    }
    const canvasFactoryInstance =
      canvasFactory ||
      new DefaultCanvasFactory({ ownerDocument: this._ownerDocument });
    const webGLContext = new WebGLContext({
      enable: enableWebGL,
    });
    const annotationStorage = includeAnnotationStorage
      ? this._transport.annotationStorage.serializable
      : null;
    
    
    if (!intentState.displayReadyCapability) {
      intentState.displayReadyCapability = createPromiseCapability();
      intentState.operatorList = {
        fnArray: [],