Oilpan: Prepare to move IdTargetObserver and IdTargetObserverRegistry to Oilpan heap.

Source/core/html/FormAssociatedElement.cpp

Index: Source/core/html/FormAssociatedElement.cpp
diff --git a/Source/core/html/FormAssociatedElement.cpp b/Source/core/html/FormAssociatedElement.cpp
index 6a809afb50a7567c789f3638adfe350edbdea576..5304066ac502df70aa45302b188b0fb5c2546578 100644
--- a/Source/core/html/FormAssociatedElement.cpp
+++ b/Source/core/html/FormAssociatedElement.cpp
@@ -36,12 +36,11 @@ namespace WebCore {
 
 using namespace HTMLNames;
 
-// FIXME: Oilpan: IdTargetObserver should be on-heap.
-class FormAttributeTargetObserver : public NoBaseWillBeGarbageCollectedFinalized<FormAttributeTargetObserver>, public IdTargetObserver {
+class FormAttributeTargetObserver : public IdTargetObserver {
     WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
 public:
     static PassOwnPtrWillBeRawPtr<FormAttributeTargetObserver> create(const AtomicString& id, FormAssociatedElement*);
-    void trace(Visitor* visitor) { visitor->trace(m_element); }
+    virtual void trace(Visitor*) OVERRIDE;
     virtual void idTargetChanged() OVERRIDE;
 
 private:
@@ -338,6 +337,12 @@ FormAttributeTargetObserver::FormAttributeTargetObserver(const AtomicString& id,
 {
 }
 
+void FormAttributeTargetObserver::trace(Visitor* visitor)
+{
+    visitor->trace(m_element);
+    IdTargetObserver::trace(visitor);
+}
+
 void FormAttributeTargetObserver::idTargetChanged()
 {
     m_element->formAttributeTargetChanged();