stylo: Include content rules from HTMLTableCellElement::WalkContentStyleRules

This also removes the TABLE_ATTRS_DIRTY optimization. Constructing nsMappedAttributes isn't really expensive and we do it all the time anyway.

components/style/gecko/wrapper.rs

@@ -33,6 +33,7 @@ use gecko_bindings::bindings::Gecko_ClassOrClassList;
 use gecko_bindings::bindings::Gecko_ElementHasAnimations;
 use gecko_bindings::bindings::Gecko_ElementHasCSSAnimations;
 use gecko_bindings::bindings::Gecko_GetAnimationRule;
+use gecko_bindings::bindings::Gecko_GetExtraContentStyleDeclarations;
 use gecko_bindings::bindings::Gecko_GetHTMLPresentationAttrDeclarationBlock;
 use gecko_bindings::bindings::Gecko_GetStyleAttrDeclarationBlock;
 use gecko_bindings::bindings::Gecko_GetStyleContext;
@@ -618,6 +619,13 @@ impl<'le> PresentationalHintsSynthetizer for GeckoElement<'le> {
                 ApplicableDeclarationBlock::from_declarations(Clone::clone(decl), ServoCascadeLevel::PresHints)
             );
         }
+        let declarations = unsafe { Gecko_GetExtraContentStyleDeclarations(self.0) };
+        let declarations = declarations.and_then(|s| s.as_arc_opt());
+        if let Some(decl) = declarations {
+            hints.push(
+                ApplicableDeclarationBlock::from_declarations(Clone::clone(decl), ServoCascadeLevel::PresHints)
+            );
+        }
     }
 }
 

components/style/gecko_bindings/bindings.rs

@@ -596,6 +596,10 @@ extern "C" {
                                                              RawGeckoElementBorrowed)
      -> RawServoDeclarationBlockStrongBorrowedOrNull;
 }
+extern "C" {
+    pub fn Gecko_GetExtraContentStyleDeclarations(element: RawGeckoElementBorrowed)
+     -> RawServoDeclarationBlockStrongBorrowedOrNull;
+}
 extern "C" {
     pub fn Gecko_GetAnimationRule(aElement: RawGeckoElementBorrowed,
                                   aPseudoTag: *mut nsIAtom,