Cleanup RootCollection methods

The methods `root` and `unroot` should both be unsafe and take
a `*const Reflector`.

components/script/dom/bindings/js.rs

@@ -495,27 +495,24 @@ impl RootCollection {
     }
 
     /// Start tracking a stack-based root
-    fn root(&self, untracked_reflector: *const Reflector) {
+    unsafe fn root(&self, untracked_reflector: *const Reflector) {
         debug_assert!(thread_state::get().is_script());
-        unsafe {
-            let mut roots = &mut *self.roots.get();
-            roots.push(untracked_reflector);
-            assert!(!(*untracked_reflector).get_jsobject().is_null())
-        }
+        let mut roots = &mut *self.roots.get();
+        roots.push(untracked_reflector);
+        assert!(!(*untracked_reflector).get_jsobject().is_null())
     }
 
-    /// Stop tracking a stack-based root, asserting if the reflector isn't found
-    fn unroot<T: Reflectable>(&self, rooted: &Root<T>) {
+    /// Stop tracking a stack-based reflector, asserting if it isn't found.
+    unsafe fn unroot(&self, tracked_reflector: *const Reflector) {
+        assert!(!tracked_reflector.is_null());
+        assert!(!(*tracked_reflector).get_jsobject().is_null());
         debug_assert!(thread_state::get().is_script());
-        unsafe {
-            let mut roots = &mut *self.roots.get();
-            let old_reflector = &*rooted.reflector();
-            match roots.iter().rposition(|r| *r == old_reflector) {
-                Some(idx) => {
-                    roots.remove(idx);
-                },
-                None => panic!("Can't remove a root that was never rooted!"),
-            }
+        let mut roots = &mut *self.roots.get();
+        match roots.iter().rposition(|r| *r == tracked_reflector) {
+            Some(idx) => {
+                roots.remove(idx);
+            },
+            None => panic!("Can't remove a root that was never rooted!"),
         }
     }
 }
@@ -618,7 +615,7 @@ impl<T: Reflectable> Clone for Root<T> {
 impl<T: Reflectable> Drop for Root<T> {
     fn drop(&mut self) {
         unsafe {
-            (*self.root_list).unroot(self);
+            (*self.root_list).unroot(self.reflector());
         }
     }
 }