Introduce Node::containingTreeScope(), which asserts that the node's root is a tree scope

third_party/WebKit/Source/core/dom/Element.cpp

Index: third_party/WebKit/Source/core/dom/Element.cpp
diff --git a/third_party/WebKit/Source/core/dom/Element.cpp b/third_party/WebKit/Source/core/dom/Element.cpp
index 7c0ce545a2e190f042784245f69865a1003d0b39..f01ea115c29f67fe68fcde5dea822cc767b52016 100644
--- a/third_party/WebKit/Source/core/dom/Element.cpp
+++ b/third_party/WebKit/Source/core/dom/Element.cpp
@@ -2224,7 +2224,7 @@ void Element::parseAttribute(const QualifiedName& name, const AtomicString&, con
         int tabindex = 0;
         if (value.isEmpty()) {
             clearTabIndexExplicitlyIfNeeded();
-            if (treeScope().adjustedFocusedElement() == this) {
+            if (isInTreeScope() && rootTreeScope().adjustedFocusedElement() == this) {
                 // We might want to call blur(), but it's dangerous to dispatch
                 // events here.
                 document().setNeedsFocusedElementCheck();
@@ -2422,7 +2422,7 @@ void Element::updateFocusAppearance(SelectionBehaviorOnFocus selectionBehavior)
 void Element::blur()
 {
     cancelFocusAppearanceUpdate();
-    if (treeScope().adjustedFocusedElement() == this) {
+    if (isInTreeScope() && rootTreeScope().adjustedFocusedElement() == this) {
         Document& doc = document();
         if (doc.page())
             doc.page()->focusController().setFocusedElement(0, doc.frame());
@@ -3144,7 +3144,7 @@ inline void Element::updateId(const AtomicString& oldId, const AtomicString& new
     if (oldId == newId)
         return;
 
-    updateId(treeScope(), oldId, newId);
+    updateId(rootTreeScope(), oldId, newId);
 }
 
 inline void Element::updateId(TreeScope& scope, const AtomicString& oldId, const AtomicString& newId)