Bug 1364850: Move PseudoElement to be just another combinator in selectors. r=bholley

MozReview-Commit-ID: 8OoOIodkKJ5
Signed-off-by: Emilio Cobos Álvarez <emilio@crisal.io>

components/selectors/tree.rs

@@ -123,6 +123,14 @@ impl<T> MatchAttr for T where T: MatchAttrGeneric, T::Impl: SelectorImpl<AttrVal
 pub trait Element: MatchAttr + Sized {
     fn parent_element(&self) -> Option<Self>;
 
+    /// The parent of a given pseudo-element, after matching a pseudo-element
+    /// selector.
+    ///
+    /// This is guaranteed to be called in a pseudo-element.
+    fn pseudo_element_originating_element(&self) -> Option<Self> {
+        self.parent_element()
+    }
+
     // Skips non-element nodes
     fn first_child_element(&self) -> Option<Self>;
 
@@ -145,6 +153,11 @@ pub trait Element: MatchAttr + Sized {
                                     flags_setter: &mut F) -> bool
         where F: FnMut(&Self, ElementSelectorFlags);
 
+    fn match_pseudo_element(&self,
+                            pe: &<Self::Impl as SelectorImpl>::PseudoElement,
+                            context: &mut MatchingContext)
+                            -> bool;
+
     fn get_id(&self) -> Option<<Self::Impl as SelectorImpl>::Identifier>;
     fn has_class(&self, name: &<Self::Impl as SelectorImpl>::ClassName) -> bool;