Serialize url as string if shorter

Author: devongovett

src/lib.rs

@@ -1047,6 +1047,8 @@ mod tests {
 
     minify_test(".foo { background: url('img-sprite.png') no-repeat bottom right }", ".foo{background:url(img-sprite.png) 100% 100% no-repeat}");
     minify_test(".foo { background: transparent }", ".foo{background:#0000}");
+
+    minify_test(".foo { background: url(\"data:image/svg+xml,%3Csvg width='168' height='24' xmlns='http://www.w3.org/2000/svg'%3E%3C/svg%3E\") }", ".foo{background:url(\"data:image/svg+xml,%3Csvg width='168' height='24' xmlns='http://www.w3.org/2000/svg'%3E%3C/svg%3E\")}");
   }
 
   #[test]

src/values/image.rs

@@ -84,7 +84,26 @@ impl ToCss for Image {
     match self {
       None => dest.write_str("none"),
       Url(url) => {
-        Token::UnquotedUrl(CowRcStr::from(url.as_ref())).to_css(dest)
+        if dest.minify {
+          let mut buf = String::new();
+          Token::UnquotedUrl(CowRcStr::from(url.as_ref())).to_css(&mut buf)?;
+
+          // If the unquoted url is longer than it would be quoted (e.g. `url("...")`)
+          // then serialize as a string and choose the shorter version.
+          if buf.len() > url.len() + 7 {
+            let mut buf2 = String::new();
+            serialize_string(url, &mut buf2)?;
+            if buf2.len() + 5 < buf.len() {
+              dest.write_str("url(")?;
+              dest.write_str(&buf2)?;
+              return dest.write_char(')')
+            }
+          }
+
+          dest.write_str(&buf)
+        } else {
+          Token::UnquotedUrl(CowRcStr::from(url.as_ref())).to_css(dest)
+        }
       }
       Gradient(grad) => grad.to_css(dest),
       ImageSet(image_set) => image_set.to_css(dest)