Auto merge of #10402 - mbrubeck:make_mut, r=pcwalton

Avoid unnecessary Arc::clone and Arc::make_mut

r? @pcwalton

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components/layout/construct.rs

@@ -973,7 +973,7 @@ impl<'a, ConcreteThreadSafeLayoutNode: ThreadSafeLayoutNode>
                 block_flow));
         let fragment = Fragment::from_opaque_node_and_style(node.opaque(),
                                                             node.get_pseudo_element_type().strip(),
-                                                            modified_style.clone(),
+                                                            modified_style,
                                                             node.selected_style().clone(),
                                                             node.restyle_damage(),
                                                             fragment_info);

components/style/properties.mako.rs

@@ -7017,6 +7017,18 @@ pub fn modify_border_style_for_inline_sides(style: &mut Arc<ServoComputedValues>
                                             is_first_fragment_of_element: bool,
                                             is_last_fragment_of_element: bool) {
     fn modify_side(style: &mut Arc<ServoComputedValues>, side: PhysicalSide) {
+        {
+            let border = &style.border;
+            let current_style = match side {
+                PhysicalSide::Left =>   (border.border_left_width,   border.border_left_style),
+                PhysicalSide::Right =>  (border.border_right_width,  border.border_right_style),
+                PhysicalSide::Top =>    (border.border_top_width,    border.border_top_style),
+                PhysicalSide::Bottom => (border.border_bottom_width, border.border_bottom_style),
+            };
+            if current_style == (Au(0), BorderStyle::none) {
+                return;
+            }
+        }
         let mut style = Arc::make_mut(style);
         let border = Arc::make_mut(&mut style.border);
         match side {