layout: Stop mutating the style data from layout.

This is part of #16982.

Right now we have some code that tries to cache stuff in the style data during
layout.

This code is extremely rarely executed, only for `<details>` and `<summary>`.

I think if we really really want to cache these, we should find a place in the
layout data for it.

For now, let's move it away (and all the other layout code) from mutating the
style data from layout.

1 files changed, 4 insertions, 2 deletions

diff --git a/components/script/layout_wrapper.rs b/components/script/layout_wrapper.rs
index fca0f0949eb..5241d01785d 100644
--- a/components/script/layout_wrapper.rs
+++ b/components/script/layout_wrapper.rs
@@ -30,7 +30,7 @@
 
 #![allow(unsafe_code)]
 
-use atomic_refcell::AtomicRefCell;
+use atomic_refcell::{AtomicRef, AtomicRefCell};
 use dom::bindings::inheritance::{CharacterDataTypeId, ElementTypeId};
 use dom::bindings::inheritance::{HTMLElementTypeId, NodeTypeId};
 use dom::bindings::js::LayoutJS;
@@ -1092,8 +1092,10 @@ impl<'le> ThreadSafeLayoutElement for ServoThreadSafeLayoutElement<'le> {
         self.element.get_attr(namespace, name)
     }
 
-    fn get_style_data(&self) -> Option<&AtomicRefCell<ElementData>> {
+    fn style_data(&self) -> AtomicRef<ElementData> {
         self.element.get_data()
+            .expect("Unstyled layout node?")
+            .borrow()
     }
 }