Commented out "url(...)" references in .css files are not ignored

[ethanrubinson]

Example
If you have a .css file with the following definition included in a browser.json file, the fonts/et-line.woff url reference is still attempted to be resolved.

src: url('fonts/et-line.eot') format('embedded-opentype'),
		/*url('fonts/et-line.woff') format('woff'),*/
 		url('fonts/et-line.ttf') format('truetype'),
 		url('fonts/et-line.svg#et-line') format('svg');