Bug 1444905: Remove scoped style support from the old style system. r=xidorn,smaug

Summary: It uses two node bits that can be better suited for something else.

Reviewers: xidorn, smaug

Bug #: 1444905

Differential Revision: https://phabricator.services.mozilla.com/D709

MozReview-Commit-ID: HIPDtHm6xpM

dom/base/Element.cpp

@@ -1712,11 +1712,6 @@ Element::BindToTree(nsIDocument* aDocument, nsIContent* aParent,
     if (ShadowRoot* shadowRootParent = ShadowRoot::FromNode(parent)) {
       parent = shadowRootParent->GetHost();
     }
-
-    bool inStyleScope = parent->IsElementInStyleScope();
-
-    SetIsElementInStyleScope(inStyleScope);
-    SetIsElementInStyleScopeFlagOnShadowTree(inStyleScope);
   }
 
   // This has to be here, rather than in nsGenericHTMLElement::BindToTree,