Verifies that mixed content issue is created from mixed content XMLHttpRequest.

PASS: requestIds match
PASS: frameIds match
Inspector issue: {
    issue : {
        code : MixedContentIssue
        details : {
            mixedContentIssueDetails : {
                frame : {
                    frameId : <string>
                }
                insecureURL : http://devtools.test:8000/inspector-protocol/resources/request-data.js
                mainResourceURL : https://devtools.test:8443/inspector-protocol/resources/mixed-content-xhr.html
                request : {
                    requestId : <string>
                    url : http://devtools.test:8000/inspector-protocol/resources/request-data.js
                }
                resolutionStatus : MixedContentBlocked
                resourceType : XMLHttpRequest
            }
        }
    }
}