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

Source/core/dom/ContainerNode.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2013 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 1066 matching lines @@
             document().styleEngine().pseudoStateChangedForElement(CSSSelector::PseudoFocus, *toElement(this));
         else if (computedStyle()->affectedByFocus())
             setNeedsStyleRecalc(LocalStyleChange, StyleChangeReasonForTracing::createWithExtraData(StyleChangeReason::PseudoClass, StyleChangeExtraData::Focus));
     }
 
     LayoutTheme::theme().controlStateChanged(*layoutObject(), FocusControlState);
 }
 
 void ContainerNode::setFocus(bool received)
 {
+    // Recurse up author shadow trees to mark shadow hosts if it matches :focus.
+    // TODO(kochi): Handle UA shadows which marks multiple nodes as focused such as
+    // <input type="date"> the same way as author shadow.
+    if (ShadowRoot* root = containingShadowRoot()) {
+        if (root->type() == ShadowRoot::OpenShadowRoot)
+            shadowHost()->setFocus(received);
+    }
+
+    // If this is an author shadow host and indirectly focused (has focused element within
+    // its shadow root), update focus.
+    if (isElementNode() && document().focusedElement() && document().focusedElement() != this) {
+        if (toElement(this)->shadowRoot())
+            received = received && toElement(this)->shadowRoot()->delegatesFocus();
+    }
+
     if (focused() == received)
         return;
 
     Node::setFocus(received);
 
     focusStateChanged();
 
     if (layoutObject() || received)
         return;
 
@@ skipping 410 matching lines @@
         return true;
 
     if (node->isElementNode() && toElement(node)->shadow())
         return true;
 
     return false;
 }
 #endif
 
 } // namespace blink