stylo: Convert pseudo-elements to an Atom wrapper.

ports/geckolib/sanity_checks.rs

@@ -42,3 +42,28 @@ fn assert_restyle_hints_match() {
     check_enum_value_non_static!(nsRestyleHint::eRestyle_SomeDescendants, RESTYLE_DESCENDANTS.bits());
     check_enum_value_non_static!(nsRestyleHint::eRestyle_LaterSiblings, RESTYLE_LATER_SIBLINGS.bits());
 }
+
+// Note that we can't call each_pseudo_element, parse_pseudo_element, or
+// similar, because we'd need the foreign atom symbols to link.
+#[test]
+fn assert_basic_pseudo_elements() {
+    let mut saw_before = false;
+    let mut saw_after = false;
+
+    macro_rules! pseudo_element {
+        (":before", $atom:expr, false) => {
+            saw_before = true;
+        };
+        (":after", $atom:expr, false) => {
+            saw_after = true;
+        };
+        ($pseudo_str_with_colon:expr, $atom:expr, $is_anon_box:expr) => {
+            // Do nothing
+        };
+    }
+
+    include!("../../components/style/generated/gecko_pseudo_element_helper.rs");
+
+    assert!(saw_before);
+    assert!(saw_after);
+}

ports/geckolib/string_cache/lib.rs

@@ -134,6 +134,21 @@ impl WeakAtom {
     }
 }
 
+impl fmt::Debug for WeakAtom {
+    fn fmt(&self, w: &mut fmt::Formatter) -> fmt::Result {
+        write!(w, "Gecko WeakAtom({:p}, {})", self, self)
+    }
+}
+
+impl fmt::Display for WeakAtom {
+    fn fmt(&self, w: &mut fmt::Formatter) -> fmt::Result {
+        for c in self.chars() {
+            try!(write!(w, "{}", c.unwrap_or(char::REPLACEMENT_CHARACTER)))
+        }
+        Ok(())
+    }
+}
+
 impl Atom {
     pub unsafe fn with<F>(ptr: *mut nsIAtom, callback: &mut F) where F: FnMut(&Atom) {
         let atom = Atom(WeakAtom::new(ptr));
@@ -217,16 +232,15 @@ impl Deserialize for Atom {
 
 impl fmt::Debug for Atom {
     fn fmt(&self, w: &mut fmt::Formatter) -> fmt::Result {
-        write!(w, "Gecko Atom {:p}", self.0)
+        write!(w, "Gecko Atom({:p}, {})", self.0, self)
     }
 }
 
 impl fmt::Display for Atom {
     fn fmt(&self, w: &mut fmt::Formatter) -> fmt::Result {
-        for c in self.chars() {
-            try!(write!(w, "{}", c.unwrap_or(char::REPLACEMENT_CHARACTER)))
+        unsafe {
+            (&*self.0).fmt(w)
         }
-        Ok(())
     }
 }