1 files changed, 30 insertions, 9 deletions

diff --git a/components/script/dom/bindings/js.rs b/components/script/dom/bindings/js.rs
index f7208237cc1..a0c099769f0 100644
--- a/components/script/dom/bindings/js.rs
+++ b/components/script/dom/bindings/js.rs
@@ -70,6 +70,15 @@ pub struct Temporary<T> {
     _js_ptr: *mut JSObject,
 }
 
+impl<T> Clone for Temporary<T> {
+    fn clone(&self) -> Temporary<T> {
+        Temporary {
+            inner: self.inner,
+            _js_ptr: self._js_ptr,
+        }
+    }
+}
+
 impl<T> PartialEq for Temporary<T> {
     fn eq(&self, other: &Temporary<T>) -> bool {
         self.inner == other.inner
@@ -92,10 +101,12 @@ impl<T: Reflectable> Temporary<T> {
 
     /// Create a stack-bounded root for this value.
     pub fn root(self) -> Root<T> {
-        let collection = StackRoots.get().unwrap();
-        unsafe {
-            Root::new(&**collection, &self.inner)
-        }
+        StackRoots.with(|ref collection| {
+            let RootCollectionPtr(collection) = collection.get().unwrap();
+            unsafe {
+                Root::new(&*collection, &self.inner)
+            }
+        })
     }
 
     unsafe fn inner(&self) -> JS<T> {
@@ -114,6 +125,8 @@ pub struct JS<T> {
     ptr: *const T
 }
 
+impl<T> Copy for JS<T> {}
+
 impl<T> PartialEq for JS<T> {
     #[allow(unrooted_must_root)]
     fn eq(&self, other: &JS<T>) -> bool {
@@ -151,10 +164,12 @@ impl<T: Reflectable> JS<T> {
 
     /// Root this JS-owned value to prevent its collection as garbage.
     pub fn root(&self) -> Root<T> {
-        let collection = StackRoots.get().unwrap();
-        unsafe {
-            Root::new(&**collection, self)
-        }
+        StackRoots.with(|ref collection| {
+            let RootCollectionPtr(collection) = collection.get().unwrap();
+            unsafe {
+                Root::new(&*collection, self)
+            }
+        })
     }
 }
 
@@ -270,7 +285,7 @@ impl<T: Reflectable> MutNullableJS<T> {
             Some(inner) => inner,
             None => {
                 let inner = cb();
-                self.assign(Some(inner));
+                self.assign(Some(inner.clone()));
                 inner
             },
         }
@@ -450,6 +465,10 @@ pub struct RootCollection {
     roots: UnsafeCell<SmallVec16<*mut JSObject>>,
 }
 
+pub struct RootCollectionPtr(pub *const RootCollection);
+
+impl Copy for RootCollectionPtr {}
+
 impl RootCollection {
     /// Create an empty collection of roots
     pub fn new() -> RootCollection {
@@ -548,6 +567,8 @@ pub struct JSRef<'a, T> {
     chain: ContravariantLifetime<'a>,
 }
 
+impl<'a, T> Copy for JSRef<'a, T> {}
+
 impl<'a, T> Clone for JSRef<'a, T> {
     fn clone(&self) -> JSRef<'a, T> {
         JSRef {