style: :dir() pseudo class now represented by enum

Fixes #19195

components/style/selector_parser.rs

@@ -8,8 +8,8 @@
 
 use cssparser::{Parser as CssParser, ParserInput};
 use selectors::parser::SelectorList;
-use std::fmt::{self, Debug};
-use style_traits::ParseError;
+use std::fmt::{self, Debug, Write};
+use style_traits::{ParseError, ToCss};
 use stylesheets::{Origin, Namespaces, UrlExtraData};
 
 /// A convenient alias for the type that represents an attribute value used for
@@ -173,3 +173,25 @@ impl<T> PerPseudoElementMap<T> {
         self.entries.iter()
     }
 }
+
+/// Values for the :dir() pseudo class
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub enum Direction {
+    /// left-to-right semantic directionality
+    Ltr,
+    /// right-to-left semantic directionality
+    Rtl,
+    /// Some other provided directionality value
+    Other(Box<str>),
+}
+
+impl ToCss for Direction {
+    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: Write {
+        let dir_str = match *self {
+            Direction::Rtl => "rtl",
+            Direction::Ltr => "ltr",
+            Direction::Other(ref other) => other,
+        };
+        dest.write_str(dir_str)
+    }
+}