Implement ShadowRoot.delegatesFocus 4/4 (match CSS :focus for shadow host)

Source/core/dom/Node.h

Index: Source/core/dom/Node.h
diff --git a/Source/core/dom/Node.h b/Source/core/dom/Node.h
index 7a6c9e5c3ee8700e2e227398f08be57881fc9bcd..04f7e28246673358db344f0b39f169c8c48e3386 100644
--- a/Source/core/dom/Node.h
+++ b/Source/core/dom/Node.h
@@ -361,6 +361,10 @@ public:
     bool active() const { return isUserActionElement() && isUserActionElementActive(); }
     bool inActiveChain() const { return isUserActionElement() && isUserActionElementInActiveChain(); }
     bool hovered() const { return isUserActionElement() && isUserActionElementHovered(); }
+    // Note: As a shadow host whose root with delegatesFocus=false may become focused state when
+    // an inner element gets focused, in that case more than one elements in a document can return
+    // true for |focused()|.  Use Element::isFocusedElementInDocument() or Document::focusedElement()
+    // to check which element is exactly focused.
     bool focused() const { return isUserActionElement() && isUserActionElementFocused(); }
 
     bool needsAttach() const { return styleChangeType() == NeedsReattachStyleChange; }