Auto merge of #8098 - bholley:dirty_from_layout, r=jdm

Track event state changes on Document and do the dirtying from layout

This is a first step in fixing #6942.

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components/script/dom/bindings/cell.rs

@@ -94,6 +94,13 @@ impl<T> DOMRefCell<T> {
             _ => None,
         }
     }
+
+    /// Version of the above that we use during restyle while the script task
+    /// is blocked.
+    pub fn borrow_mut_for_layout(&self) -> RefMut<T> {
+        debug_assert!(task_state::get().is_layout());
+        self.value.borrow_mut()
+    }
 }
 
 impl<T: JSTraceable> JSTraceable for DOMRefCell<T> {

components/script/dom/bindings/js.rs

@@ -35,6 +35,7 @@ use layout_interface::TrustedNodeAddress;
 use script_task::STACK_ROOTS;
 use std::cell::UnsafeCell;
 use std::default::Default;
+use std::hash::{Hash, Hasher};
 use std::mem;
 use std::ops::Deref;
 use std::ptr;
@@ -147,12 +148,24 @@ impl<T> PartialEq for JS<T> {
     }
 }
 
+impl<T> Eq for JS<T> {}
+
 impl<T> PartialEq for LayoutJS<T> {
     fn eq(&self, other: &LayoutJS<T>) -> bool {
         self.ptr == other.ptr
     }
 }
 
+impl<T> Eq for LayoutJS<T> {}
+
+impl<T> Hash for JS<T> {
+    fn hash<H: Hasher>(&self, state: &mut H) { self.ptr.hash(state) }
+}
+
+impl<T> Hash for LayoutJS<T> {
+    fn hash<H: Hasher>(&self, state: &mut H) { self.ptr.hash(state) }
+}
+
 impl <T> Clone for JS<T> {
     #[inline]
     #[allow(unrooted_must_root)]