Move some Element specific code from Node::detach to Element::detach.

Source/core/dom/UserActionElementSet.cpp

Index: Source/core/dom/UserActionElementSet.cpp
diff --git a/Source/core/dom/UserActionElementSet.cpp b/Source/core/dom/UserActionElementSet.cpp
index 0358e59ad080eac94800ffaf338b01c4f9f113bf..e9ec739df2157537db43a61e4dba31e329cce95e 100644
--- a/Source/core/dom/UserActionElementSet.cpp
+++ b/Source/core/dom/UserActionElementSet.cpp
@@ -40,10 +40,10 @@ UserActionElementSet::~UserActionElementSet()
 {
 }
 
-void UserActionElementSet::didDetach(Node* node)
+void UserActionElementSet::didDetach(Element& element)
 {
-    ASSERT(node->isUserActionElement());
-    clearFlags(toElement(node), IsActiveFlag | InActiveChainFlag | IsHoveredFlag);
+    ASSERT(element.isUserActionElement());
+    clearFlags(&element, IsActiveFlag | InActiveChainFlag | IsHoveredFlag);
 }
 
 #if !ENABLE(OILPAN)