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, 17 insertions, 11 deletions

diff --git a/src/components/script/dom/formdata.rs b/src/components/script/dom/formdata.rs
index 140c70a12d2..c6631699671 100644
--- a/src/components/script/dom/formdata.rs
+++ b/src/components/script/dom/formdata.rs
@@ -5,7 +5,7 @@
 use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
 use dom::bindings::error::{Fallible};
 use dom::bindings::codegen::BindingDeclarations::FormDataBinding;
-use dom::bindings::js::JS;
+use dom::bindings::js::{JS, JSRef, Temporary, OptionalUnrootable};
 use dom::blob::Blob;
 use dom::htmlformelement::HTMLFormElement;
 use dom::window::Window;
@@ -28,33 +28,39 @@ pub struct FormData {
 }
 
 impl FormData {
-    pub fn new_inherited(form: Option<JS<HTMLFormElement>>, window: JS<Window>) -> FormData {
+    pub fn new_inherited(form: Option<JSRef<HTMLFormElement>>, window: &JSRef<Window>) -> FormData {
         FormData {
             data: HashMap::new(),
             reflector_: Reflector::new(),
-            window: window,
-            form: form
+            window: window.unrooted(),
+            form: form.unrooted(),
         }
     }
 
-    pub fn new(form: Option<JS<HTMLFormElement>>, window: &JS<Window>) -> JS<FormData> {
-        reflect_dom_object(~FormData::new_inherited(form, window.clone()), window, FormDataBinding::Wrap)
+    pub fn new(form: Option<JSRef<HTMLFormElement>>, window: &JSRef<Window>) -> Temporary<FormData> {
+        reflect_dom_object(~FormData::new_inherited(form, window), window, FormDataBinding::Wrap)
     }
 
-    pub fn Constructor(window: &JS<Window>, form: Option<JS<HTMLFormElement>>)
-                       -> Fallible<JS<FormData>> {
+    pub fn Constructor(window: &JSRef<Window>, form: Option<JSRef<HTMLFormElement>>) -> Fallible<Temporary<FormData>> {
         Ok(FormData::new(form, window))
     }
+}
+
+pub trait FormDataMethods {
+    fn Append(&mut self, name: DOMString, value: &JSRef<Blob>, filename: Option<DOMString>);
+    fn Append_(&mut self, name: DOMString, value: DOMString);
+}
 
-    pub fn Append(&mut self, name: DOMString, value: &JS<Blob>, filename: Option<DOMString>) {
+impl<'a> FormDataMethods for JSRef<'a, FormData> {
+    fn Append(&mut self, name: DOMString, value: &JSRef<Blob>, filename: Option<DOMString>) {
         let blob = BlobData {
-            blob: value.clone(),
+            blob: value.unrooted(),
             name: filename.unwrap_or(~"default")
         };
         self.data.insert(name.clone(), blob);
     }
 
-    pub fn Append_(&mut self, name: DOMString, value: DOMString) {
+    fn Append_(&mut self, name: DOMString, value: DOMString) {
         self.data.insert(name, StringData(value));
     }
 }