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

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

Index: third_party/WebKit/Source/core/dom/Node.cpp
diff --git a/third_party/WebKit/Source/core/dom/Node.cpp b/third_party/WebKit/Source/core/dom/Node.cpp
index cdcbf0a9ba1275722a2cca800bcf88e3cdfb29d4..f20b23f7a0a8beb0c4ea8e829d85170494fc3f63 100644
--- a/third_party/WebKit/Source/core/dom/Node.cpp
+++ b/third_party/WebKit/Source/core/dom/Node.cpp
@@ -843,6 +843,15 @@ bool Node::isShadowIncludingInclusiveAncestorOf(const Node* node) const
     return false;
 }
 
+Node* Node::retarget(const Node& target) const
+{
+    for (const Node* ancestor = ⌖ ancestor; ancestor = ancestor->shadowHost()) {
+        if (treeScope() == ancestor->treeScope())
+            return const_cast<Node*>(ancestor);
+    }
+    return nullptr;
+}
+
 bool Node::containsIncludingHostElements(const Node& node) const
 {
     const Node* current = &node;