sub _wait_while_busy {
    my $self = shift;
    my $agent = $self->{agent};

    # The documentation isn't clear on this.
    # The DocumentComplete event roughly says:
    # the event gets fired (for each frame) after ReadyState == 4
    # we might need to check if the first one has frames
    # and do some more checking.
    my $sleep = 4; # 0.4;
#    while ( $agent->{Busy} == 1 ) { $sleep and sleep( $sleep ) }
#    return unless $agent->{ReadyState};
    while ( $agent->{ReadyState} <= 2 ) {
        $sleep and sleep( $sleep );
    }

    $self->{ $_ } = undef for qw( forms cur_form links images );
    return $self->success;
}