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, 2 insertions, 3 deletions

diff --git a/src/components/main/layout/construct.rs b/src/components/main/layout/construct.rs
index 72ce8e09b97..46f5c5ef287 100644
--- a/src/components/main/layout/construct.rs
+++ b/src/components/main/layout/construct.rs
@@ -45,7 +45,6 @@ use layout::wrapper::{Before, BeforeBlock, After, AfterBlock, Normal};
 
 use gfx::display_list::OpaqueNode;
 use gfx::font_context::FontContext;
-use script::dom::bindings::codegen::InheritTypes::TextCast;
 use script::dom::bindings::js::JS;
 use script::dom::element::{HTMLIFrameElementTypeId, HTMLImageElementTypeId};
 use script::dom::element::{HTMLObjectElementTypeId};
@@ -1064,8 +1063,8 @@ impl<'ln> NodeUtils for ThreadSafeLayoutNode<'ln> {
         match self.type_id() {
             Some(TextNodeTypeId) => {
                 unsafe {
-                    let text: JS<Text> = TextCast::to(self.get_jsmanaged()).unwrap();
-                    if !is_whitespace(text.get().characterdata.data) {
+                    let text: JS<Text> = self.get_jsmanaged().transmute_copy();
+                    if !is_whitespace((*text.unsafe_get()).characterdata.data) {
                         return false
                     }