Add some fmt::Debug implementations

components/script/dom/element.rs

@@ -79,6 +79,7 @@ use std::borrow::Cow;
 use std::cell::{Cell, Ref};
 use std::convert::TryFrom;
 use std::default::Default;
+use std::fmt;
 use std::mem;
 use std::sync::Arc;
 use std::sync::atomic::{AtomicUsize, Ordering};
@@ -115,6 +116,16 @@ pub struct Element {
     atomic_flags: AtomicElementFlags,
 }
 
+impl fmt::Debug for Element {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        try!(write!(f, "<{}", self.local_name));
+        if let Some(ref id) = *self.id_attribute.borrow() {
+            try!(write!(f, " id={}", id));
+        }
+        write!(f, ">")
+    }
+}
+
 #[derive(PartialEq, HeapSizeOf)]
 pub enum ElementCreator {
     ParserCreated,