Set-Cookie path should not be case-insensitive

[MegatronKing]

Because the Uri path is case-sensitive, the path value of Set-Cookie should also be case-sensitive. But I checked the dart code and it was forcibly converted to lowercase.

String parseAttributeValue() {
  int start = index;
  while (!done()) {
    if (s[index] == ";") break;
    index++;
  }
  return s.substring(start, index).trim().toLowerCase();
}

In addition, the browser also maintains case sensitivity when saving the cookie path.