Tests CSS warnings are properly exposed.

Invalid CSS property declaration at: # console-css-warnings.html:10
Invalid CSS property declaration at: { console-css-warnings.html:15
Invalid CSS property declaration at: # console-css-warnings.html:18
Invalid CSS property declaration at: # console-css-warnings.html:22
Invalid CSS property declaration at: # console-css-warnings.html:32
Unexpected CSS token: @ console-css-warnings.html:33
Unexpected CSS token: { console-css-warnings.html:37
Unexpected CSS token: { console-css-warnings.html:38
Unexpected CSS token: { console-css-warnings.html:39
Unexpected CSS token: { console-css-warnings.html:40
Unexpected CSS token: @ console-css-warnings.html:44