Tests CSS.getEnvironmentVariables
env(): {
    id : <number>
    result : {
        environmentVariables : {
            keyboard-inset-bottom : <string>
            keyboard-inset-height : <string>
            keyboard-inset-left : <string>
            keyboard-inset-right : <string>
            keyboard-inset-top : <string>
            keyboard-inset-width : <string>
            preferred-text-scale : <string>
            safe-area-inset-bottom : <string>
            safe-area-inset-left : <string>
            safe-area-inset-right : <string>
            safe-area-inset-top : <string>
            safe-area-max-inset-bottom : <string>
            safe-area-max-inset-left : <string>
            safe-area-max-inset-right : <string>
            safe-area-max-inset-top : <string>
        }
    }
    sessionId : <string>
}