Configuration:
- PDF.js version: 2.0.550

Steps to reproduce the problem:
1. Render document in SVG mode `renderMode="svg"`

What is the expected behavior? (add screenshot)
Rendering annotations same way as they rendered on canvas

What went wrong? (add screenshot)
```
Warning: Unimplemented operator beginAnnotations
Warning: Unimplemented operator endAnnotations
```
workerId,
            worker.port
          );
          messageHandler.postMessageTransfers = worker.postMessageTransfers;
          const transport = new WorkerTransport(
            messageHandler,
            task,
            networkStream,
            params
          );
          task._transport = transport;
          messageHandler.send("Ready", null);
        }
      );
    })
    .catch(task._capability.reject);
  return task;
}
/**
 * Starts fetching of specified PDF document/data.
 *
 * @param {PDFWorker} worker
 * @param {Object} source
 * @param {PDFDataRangeTransport} pdfDataRangeTransport
 * @param {string} docId - Unique document ID, used in `MessageHandler`.
 * @returns {Promise} A promise that is resolved when the worker ID of the
 *   `MessageHandler` is known.
 * @private
 */
function _fetchDocument(worker, source, pdfDataRangeTransport, docId) {