Tests that execution contexts are reported for iframes that don't have src attribute.
{
    method : Runtime.executionContextCreated
    params : {
        context : {
            auxData : {
                frameId : <string>
                isDefault : true
                type : default
            }
            id : <number>
            name : 
            origin : http://devtools.test:8000
        }
    }
    sessionId : <string>
}
{
    method : Runtime.executionContextCreated
    params : {
        context : {
            auxData : {
                frameId : <string>
                isDefault : true
                type : default
            }
            id : <number>
            name : 
            origin : http://devtools.test:8000
        }
    }
    sessionId : <string>
}