Checks that proxies in JSONML are rejected by custom formatters
Test proxy child in header JSONML..
{
    method : Runtime.consoleAPICalled
    params : {
        args : [
            [0] : {
                type : string
                value : Custom Formatter Failed: Uncaught Proxy values are not allowed in JSONML
            }
        ]
        executionContextId : <executionContextId>
        timestamp : <timestamp>
        type : error
    }
}
No customPreview generated
Test proxy attributes in header JSONML..
{
    method : Runtime.consoleAPICalled
    params : {
        args : [
            [0] : {
                type : string
                value : Custom Formatter Failed: Uncaught Proxy values are not allowed in JSONML
            }
        ]
        executionContextId : <executionContextId>
        timestamp : <timestamp>
        type : error
    }
}
No customPreview generated
Test proxy array child masquerading as tag..
{
    method : Runtime.consoleAPICalled
    params : {
        args : [
            [0] : {
                type : string
                value : Custom Formatter Failed: Uncaught Proxy values are not allowed in JSONML
            }
        ]
        executionContextId : <executionContextId>
        timestamp : <timestamp>
        type : error
    }
}
No customPreview generated
Test proxy attributes in object tag..
{
    method : Runtime.consoleAPICalled
    params : {
        args : [
            [0] : {
                type : string
                value : Custom Formatter Failed: Uncaught Proxy values are not allowed in JSONML
            }
        ]
        executionContextId : <executionContextId>
        timestamp : <timestamp>
        type : error
    }
}
No customPreview generated
Test proxy child in body JSONML..
customPreview: ["span",{},"Header ok"]
{
    method : Runtime.consoleAPICalled
    params : {
        args : [
            [0] : {
                type : string
                value : Custom Formatter Failed: Uncaught Proxy values are not allowed in JSONML
            }
        ]
        executionContextId : <executionContextId>
        timestamp : <timestamp>
        type : error
    }
}
{
    id : <messageId>
    result : {
        result : {
            type : undefined
        }
    }
}
Test formatting a proxy object itself (allowed)..
customPreview: ["span",{},"Proxy formatted: ","proxyObject"]
