Remove use of some other unstable features

components/layout_2020/flow/inline.rs

@@ -303,7 +303,11 @@ impl InlineFormattingContext {
                                     panic!("display:none does not generate an abspos box")
                                 },
                             };
-                        let hoisted_box = box_.clone().to_hoisted(initial_start_corner, tree_rank);
+                        let hoisted_box = AbsolutelyPositionedBox::to_hoisted(
+                            box_.clone(),
+                            initial_start_corner,
+                            tree_rank,
+                        );
                         let hoisted_fragment = hoisted_box.fragment.clone();
                         ifc.push_hoisted_box_to_positioning_context(hoisted_box);
                         ifc.current_nesting_level.fragments_so_far.push(
@@ -786,7 +790,7 @@ impl TextRun {
                     glyphs,
                     text_decoration_line: ifc.current_nesting_level.text_decoration_line,
                 }));
-            if runs.is_empty() {
+            if runs.as_slice().is_empty() {
                 break;
             } else {
                 // New line

components/layout_2020/flow/mod.rs

@@ -315,7 +315,8 @@ impl BlockLevelBox {
                 ))
             },
             BlockLevelBox::OutOfFlowAbsolutelyPositionedBox(box_) => {
-                let hoisted_box = box_.clone().to_hoisted(Vec2::zero(), tree_rank);
+                let hoisted_box =
+                    AbsolutelyPositionedBox::to_hoisted(box_.clone(), Vec2::zero(), tree_rank);
                 let hoisted_fragment = hoisted_box.fragment.clone();
                 positioning_context.push(hoisted_box);
                 Fragment::AbsoluteOrFixedPositioned(AbsoluteOrFixedPositionedFragment {

components/layout_2020/lib.rs

@@ -3,8 +3,6 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 #![deny(unsafe_code)]
-#![feature(arbitrary_self_types)]
-#![feature(exact_size_is_empty)]
 
 #[macro_use]
 extern crate serde;

components/layout_2020/positioned.rs

@@ -100,7 +100,7 @@ impl AbsolutelyPositionedBox {
     }
 
     pub(crate) fn to_hoisted(
-        self: Arc<Self>,
+        self_: Arc<Self>,
         initial_start_corner: Vec2<Length>,
         tree_rank: usize,
     ) -> HoistedAbsolutelyPositionedBox {
@@ -124,7 +124,7 @@ impl AbsolutelyPositionedBox {
             }
         }
 
-        let box_offsets = self.contents.style.box_offsets();
+        let box_offsets = self_.contents.style.box_offsets();
         HoistedAbsolutelyPositionedBox {
             tree_rank,
             box_offsets: Vec2 {
@@ -140,7 +140,7 @@ impl AbsolutelyPositionedBox {
                 ),
             },
             fragment: ArcRefCell::new(None),
-            absolutely_positioned_box: self,
+            absolutely_positioned_box: self_,
         }
     }
 }