Bug 1449089 part 1 - Make :-moz-native-anonymous and :-moz-use-shadow-tree-root matches in Rust code. r=emilio

:-moz-native-anonymous can just use is_in_native_anonymous_subtree()
which is an existing function duplicating IsInNativeAnonymousSubtree().

IsRootOfUseElementShadowTree() in C++ code only has a single reference
from nsCSSPseudoClasses::MatchesElement() so we can just move it to the
Rust side. And actually Rust code has existing duplicate logic for
blocks_ancestor_combinators().

MozReview-Commit-ID: 8M1hHrYJT6Y

--HG--
extra : rebase_source : bf53ac7d8b15b0d1f7447a6056986d89b1cb4e57

dom/base/nsIContent.h

@@ -246,14 +246,6 @@ public:
     return IsInNativeAnonymousSubtree() || (!IsInShadowTree() && GetBindingParent() != nullptr);
   }
 
-  /*
-   * Return true if this node is the shadow root of an use-element shadow tree.
-   */
-  bool IsRootOfUseElementShadowTree() const {
-    return GetParent() && GetParent()->IsSVGElement(nsGkAtoms::use) &&
-           IsRootOfAnonymousSubtree();
-  }
-
   /**
    * Return true iff this node is in an HTML document (in the HTML5 sense of
    * the term, i.e. not in an XHTML/XML document).

layout/style/nsCSSPseudoClasses.cpp

@@ -295,10 +295,6 @@ nsCSSPseudoClasses::StringPseudoMatches(const mozilla::dom::Element* aElement,
 nsCSSPseudoClasses::MatchesElement(Type aType, const dom::Element* aElement)
 {
   switch (aType) {
-    case CSSPseudoClassType::mozNativeAnonymous:
-      return Some(aElement->IsInNativeAnonymousSubtree());
-    case CSSPseudoClassType::mozUseShadowTreeRoot:
-      return Some(aElement->IsRootOfUseElementShadowTree());
     case CSSPseudoClassType::mozTableBorderNonzero: {
       if (!aElement->IsHTMLElement(nsGkAtoms::table)) {
         return Some(false);