Tests that invalid rule inside @-rule doesn't break source code matching (http://crbug.com/317499).

[expanded] 
element.style { ()

[expanded] 
#main { (styles-sour…per.html:25 -> styles-source-lines-recovery-helper.html:25:8)
    color: white;

[expanded] 
#main { (styles-sour…per.html:16 -> styles-source-lines-recovery-helper.html:16:8)
/-- overloaded --/     color: blue;

[expanded] 
#main { (styles-sour…lper.html:7 -> styles-source-lines-recovery-helper.html:7:8)
/-- overloaded --/     color: red;

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