openRequest method
Open the request. If client
is given, that client should be used to open
the request.
This logic is platform-specific and should be implemented by the subclass.
Implementation
@override
Future<Null> openRequest([_]) async {
_registerHandlers();
// Allow the controller of this mock request to trigger an unexpected
// exception to test the handling of said exception.
if (_shouldFailToOpen) throw Exception('Mock request failed to open.');
}