Remove use of unstable box syntax.

http://www.robohornet.org gives a score of 101.36 on master,
and 102.68 with this PR. The latter is slightly better,
but probably within noise level.
So it looks like this PR does not affect DOM performance.

This is expected since `Box::new` is defined as:

```rust
impl<T> Box<T> {
    #[inline(always)]
    pub fn new(x: T) -> Box<T> {
        box x
    }
}
```

With inlining, it should compile to the same as box syntax.

1 files changed, 2 insertions, 2 deletions

diff --git a/components/script/dom/testbindingpairiterable.rs b/components/script/dom/testbindingpairiterable.rs
index 5fae49893aa..2fa90f48fc6 100644
--- a/components/script/dom/testbindingpairiterable.rs
+++ b/components/script/dom/testbindingpairiterable.rs
@@ -37,10 +37,10 @@ impl Iterable for TestBindingPairIterable {
 
 impl TestBindingPairIterable {
     fn new(global: &GlobalScope) -> DomRoot<TestBindingPairIterable> {
-        reflect_dom_object(box TestBindingPairIterable {
+        reflect_dom_object(Box::new(TestBindingPairIterable {
             reflector: Reflector::new(),
             map: DomRefCell::new(vec![]),
-        }, global, TestBindingPairIterableBinding::TestBindingPairIterableWrap)
+        }), global, TestBindingPairIterableBinding::TestBindingPairIterableWrap)
     }
 
     pub fn Constructor(global: &GlobalScope) -> Fallible<DomRoot<TestBindingPairIterable>> {