Creates a new content type object setting the primary type and
sub type. The charset and additional parameters can also be set
using charset and parameters. If charset is passed and
parameters contains charset as well the passed charset will
override the value in parameters. Keys passed in parameters will be
converted to lower case. The charset entry, whether passed as charset
or in parameters, will have its value converted to lower-case.
Source
factory ContentType(String primaryType, String subType,
{String charset, Map<String, String> parameters}) {
return new _ContentType(primaryType, subType, charset, parameters);
}