Add iterators for nsStyleAutoArray

ports/geckolib/gecko_bindings/sugar/mod.rs

@@ -2,4 +2,5 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+mod ns_style_auto_array;
 mod ns_t_array;

ports/geckolib/gecko_bindings/sugar/ns_style_auto_array.rs

@@ -0,0 +1,21 @@
+use std::iter::{once, Chain, Once, IntoIterator};
+use std::slice::{IterMut};
+use structs::nsStyleAutoArray;
+
+impl<T> nsStyleAutoArray<T> {
+    pub fn iter_mut(&mut self) -> Chain<Once<&mut T>, IterMut<T>> {
+        once(&mut self.mFirstElement).chain(self.mOtherElements.iter_mut())
+    }
+
+    pub fn len(&self) -> usize {
+        1 + self.mOtherElements.len()
+    }
+}
+
+impl<'a, T> IntoIterator for &'a mut nsStyleAutoArray<T> {
+    type Item = &'a mut T;
+    type IntoIter = Chain<Once<&'a mut T>, IterMut<'a, T>>;
+    fn into_iter(self) -> Self::IntoIter {
+        self.iter_mut()
+    } 
+}