auto merge of #2101 : jdm/servo/newroot_rebase, r=Ms2ger

As described in #1764, this strategy uses the following properties:
* DOM members are `JS<T>` types. These cannot be used with being explicitly rooted, but they are required for compiler-derived trace hooks.
* Methods that take DOM type arguments receive `&[mut] JSRef<T>`. These are rooted value references that are cloneable but cannot escape.
* Methods that return DOM values use `Unrooted<T>`. These are values that may or may not be rooted elsewhere, but callers must root them in order to interact with them in any way. One unsoundness hole exists - `Unrooted` values must be rooted ASAP, or there exists the danger that JSAPI calls could be made that could cause the underlying JS value to be GCed.
* All methods are implemented on `JSRef<T>`, enforcing the requirement that all DOM values are rooted for the duration of a method call (with a few exceptions for layout-related code, which cannot root values and therefore interacts with `JS<T>` and `&T` values - this is safe under the assumption that layout code interacts with DOM nodes that are in the tree, therefore rooted, and does not run concurrently with content code)

1 files changed, 7 insertions, 4 deletions

diff --git a/src/components/script/dom/htmlunknownelement.rs b/src/components/script/dom/htmlunknownelement.rs
index a8a0b3cb41d..855b17578e5 100644
--- a/src/components/script/dom/htmlunknownelement.rs
+++ b/src/components/script/dom/htmlunknownelement.rs
@@ -4,7 +4,7 @@
 
 use dom::bindings::codegen::BindingDeclarations::HTMLUnknownElementBinding;
 use dom::bindings::codegen::InheritTypes::HTMLUnknownElementDerived;
-use dom::bindings::js::JS;
+use dom::bindings::js::{JSRef, Temporary};
 use dom::document::Document;
 use dom::element::HTMLUnknownElementTypeId;
 use dom::eventtarget::{EventTarget, NodeTargetTypeId};
@@ -27,14 +27,17 @@ impl HTMLUnknownElementDerived for EventTarget {
 }
 
 impl HTMLUnknownElement {
-    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLUnknownElement {
+    pub fn new_inherited(localName: DOMString, document: &JSRef<Document>) -> HTMLUnknownElement {
         HTMLUnknownElement {
             htmlelement: HTMLElement::new_inherited(HTMLUnknownElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLUnknownElement> {
-        let element = HTMLUnknownElement::new_inherited(localName, document.clone());
+    pub fn new(localName: DOMString, document: &JSRef<Document>) -> Temporary<HTMLUnknownElement> {
+        let element = HTMLUnknownElement::new_inherited(localName, document);
         Node::reflect_node(~element, document, HTMLUnknownElementBinding::Wrap)
     }
 }
+
+pub trait HTMLUnknownElementMethods {
+}