Tests that proper (and different) styles are returned for body elements of main document and iframe.

Main frame style:
[expanded] 
element.style { ()

[expanded] 
#main { (styles-iframe.js:2 -> styles-iframe.js:2:16)
    background: blue;

[expanded] 
div { (user agent stylesheet)
    display: block;
    unicode-bidi: isolate;

iframe style:
[expanded] 
element.style { ()

[expanded] 
body { (styles-ifra…data.html:4 -> styles-iframe-data.html:4:9)
    background: green;

[expanded] 
body { (user agent stylesheet)
    display: block;
    margin: 8px;