Verifies that CSP issue is created from a page with image source violation.

Inspector issue: {
    issue : {
        code : ContentSecurityPolicyIssue
        details : {
            contentSecurityPolicyIssueDetails : {
                blockedURL : https://thirdparty.test/network/resources/to-be-blocked.jpg
                contentSecurityPolicyViolationType : kURLViolation
                isReportOnly : false
                sourceCodeLocation : {
                    columnNumber : 0
                    lineNumber : 8
                    url : https://devtools.test:8443/inspector-protocol/resources/content-security-policy-issue-image.php
                }
                violatedDirective : img-src
            }
        }
    }
}