Make DOMRefCell use style’s copy of RefCell

components/style/refcell.rs

@@ -15,6 +15,7 @@
 
 #![allow(unsafe_code)]
 
+#[cfg(feature = "servo")] use heapsize::HeapSizeOf;
 use std::cell::{UnsafeCell, Cell};
 use std::cmp::Ordering;
 use std::fmt::{self, Debug, Display};
@@ -31,6 +32,13 @@ pub struct RefCell<T: ?Sized> {
     value: UnsafeCell<T>,
 }
 
+#[cfg(feature = "servo")]
+impl<T: HeapSizeOf> HeapSizeOf for RefCell<T> {
+    fn heap_size_of_children(&self) -> usize {
+        self.borrow().heap_size_of_children()
+    }
+}
+
 /// An enumeration of values returned from the `state` method on a `RefCell<T>`.
 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 pub enum BorrowState {
@@ -527,6 +535,18 @@ impl<'b, T: ?Sized> Ref<'b, T> {
             borrow: orig.borrow,
         }
     }
+
+    #[inline]
+    pub fn filter_map<U: ?Sized, F>(orig: Ref<'b, T>, f: F) -> Option<Ref<'b, U>>
+        where F: FnOnce(&T) -> Option<&U>
+    {
+        f(orig.value).map(move |new_value| {
+            Ref {
+                value: new_value,
+                borrow: orig.borrow,
+            }
+        })
+    }
 }
 
 impl<'b, T: ?Sized> RefMut<'b, T> {