Update the behavior of ShadowRoot.activeElement to match the latest spec

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

 /*
  * Copyright (C) 2011 Google Inc. All Rights Reserved.
  * Copyright (C) 2012 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 411 matching lines @@
 
 Element* TreeScope::adjustedFocusedElement() const
 {
     Document& document = rootNode().document();
     Element* element = document.focusedElement();
     if (!element && document.page())
         element = document.page()->focusController().focusedFrameOwnerElement(*document.frame());
     if (!element)
         return nullptr;
 
+    if (rootNode().isInV1ShadowTree()) {
+        if (Node* retargeted = rootNode().retarget(*element)) {
+            DCHECK(retargeted->isElementNode());
+            return this == &retargeted->treeScope() ? toElement(retargeted) : nullptr;
+        }
+        return nullptr;
+    }
+
     RawPtr<EventPath> eventPath = new EventPath(*element);
     for (size_t i = 0; i < eventPath->size(); ++i) {
         if (eventPath->at(i).node() == rootNode()) {
             // eventPath->at(i).target() is one of the followings:
             // - InsertionPoint
             // - shadow host
             // - Document::focusedElement()
             // So, it's safe to do toElement().
             return toElement(eventPath->at(i).target()->toNode());
         }
@@ skipping 134 matching lines @@
     visitor->trace(m_idTargetObserverRegistry);
     visitor->trace(m_selection);
     visitor->trace(m_elementsById);
     visitor->trace(m_imageMapsByName);
     visitor->trace(m_labelsByForAttribute);
     visitor->trace(m_scopedStyleResolver);
     visitor->trace(m_radioButtonGroupScope);
 }
 
 } // namespace blink