send method
Send a binary message to the platform plugins on the given channel.
Returns a Future which completes to the received response, undecoded, in binary form.
Implementation
@override
Future<ByteData?>? send(String channel, ByteData? message) {
final MessageHandler? handler = _mockHandlers[channel];
if (handler != null) return handler(message);
return _sendPlatformMessage(channel, message);
}