Auto merge of #8667 - asajeffrey:update-string-cache, r=SimonSapin

Update string cache

Updated string_cache to 0.2, and updated the dependencies that depend on string_cache.
Removed references to string_cache_plugin.
Import atom! and ns! from string_cache.
Replaced ns!("") by ns!().
Replaced ns!(XML) and co by ns!(xml) and co.
Replaced Atom::from_slice by Atom::from.
Replaced atom.as_slice() by &*atom.

r? @SimonSapin

<!-- Reviewable:start -->
[<img src="https://reviewable.io/review_button.png" height=40 alt="Review on Reviewable"/>](https://reviewable.io/reviews/servo/servo/8667)
<!-- Reviewable:end -->

1 files changed, 2 insertions, 2 deletions

diff --git a/components/layout/wrapper.rs b/components/layout/wrapper.rs
index 5c1622c3295..f76a3ea3862 100644
--- a/components/layout/wrapper.rs
+++ b/components/layout/wrapper.rs
@@ -662,7 +662,7 @@ impl<'le> ::selectors::Element for ServoLayoutElement<'le> {
             NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLAreaElement)) |
             NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLLinkElement)) => {
                 unsafe {
-                    (*self.element.unsafe_get()).get_attr_val_for_layout(&ns!(""), &atom!("href")).is_some()
+                    (*self.element.unsafe_get()).get_attr_val_for_layout(&ns!(), &atom!("href")).is_some()
                 }
             }
             _ => false,
@@ -712,7 +712,7 @@ impl<'le> ::selectors::Element for ServoLayoutElement<'le> {
     #[inline]
     fn has_servo_nonzero_border(&self) -> bool {
         unsafe {
-            match (*self.element.unsafe_get()).get_attr_for_layout(&ns!(""), &atom!("border")) {
+            match (*self.element.unsafe_get()).get_attr_for_layout(&ns!(), &atom!("border")) {
                 None | Some(&AttrValue::UInt(_, 0)) => false,
                 _ => true,
             }