[oilpan] Completely move HTMLFormControlElement's hierarchy to the managed heap

Source/core/html/HTMLFormElement.h

Index: Source/core/html/HTMLFormElement.h
diff --git a/Source/core/html/HTMLFormElement.h b/Source/core/html/HTMLFormElement.h
index 08c89696b8bce4522aec13c749bf96402844c0af..6dd669f3baf5a329ec77656cba46dd87be96e760 100644
--- a/Source/core/html/HTMLFormElement.h
+++ b/Source/core/html/HTMLFormElement.h
@@ -94,7 +94,7 @@ public:
 
     bool wasUserSubmitted() const;
 
-    HTMLFormControlElement* defaultButton() const;
+    Result<HTMLFormControlElement> defaultButton() const;
 
     bool checkValidity();
 
@@ -111,8 +111,8 @@ public:
     DEFINE_ATTRIBUTE_EVENT_LISTENER(autocomplete);
     DEFINE_ATTRIBUTE_EVENT_LISTENER(autocompleteerror);
 
-    HTMLFormControlElement* elementForAlias(const AtomicString&);
-    void addElementAlias(HTMLFormControlElement*, const AtomicString& alias);
+    Result<HTMLFormControlElement> elementForAlias(const AtomicString&);
+    void addElementAlias(Handle<HTMLFormControlElement>, const AtomicString& alias);
 
     CheckedRadioButtons& checkedRadioButtons() { return m_checkedRadioButtons; }
 
@@ -151,7 +151,7 @@ private:
     // are any invalid controls in this form.
     bool checkInvalidControlsAndCollectUnhandled(Vector<RefPtr<FormAssociatedElement> >&);
 
-    typedef HashMap<RefPtr<AtomicStringImpl>, RefPtr<HTMLFormControlElement> > AliasMap;
+    typedef HashMap<RefPtr<AtomicStringImpl>, Persistent<HTMLFormControlElement> > AliasMap;
 
     FormSubmission::Attributes m_attributes;
     OwnPtr<AliasMap> m_elementAliases;