Oilpan: add missing HTMLFormControlsCollection tracing.

Source/core/html/HTMLFormControlsCollection.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2014 Samsung Electronics. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 22 matching lines @@
 
 namespace WebCore {
 
 using namespace HTMLNames;
 
 // Since the collections are to be "live", we have to do the
 // calculation every time if anything has changed.
 
 HTMLFormControlsCollection::HTMLFormControlsCollection(ContainerNode& ownerNode)
     : HTMLCollection(ownerNode, FormControls, OverridesItemAfter)
-    , m_cachedElement(0)
+    , m_cachedElement(nullptr)
     , m_cachedElementOffsetInArray(0)
 {
     ASSERT(isHTMLFormElement(ownerNode) || isHTMLFieldSetElement(ownerNode));
     ScriptWrappable::init(this);
 }
 
 PassRefPtrWillBeRawPtr<HTMLFormControlsCollection> HTMLFormControlsCollection::create(ContainerNode& ownerNode, CollectionType)
 {
     return adoptRefWillBeNoop(new HTMLFormControlsCollection(ownerNode));
 }
@@ skipping 44 matching lines @@
             m_cachedElementOffsetInArray = i;
             return m_cachedElement;
         }
     }
     return 0;
 }
 
 void HTMLFormControlsCollection::invalidateCache(Document* oldDocument) const
 {
     HTMLCollection::invalidateCache(oldDocument);
-    m_cachedElement = 0;
+    m_cachedElement = nullptr;
     m_cachedElementOffsetInArray = 0;
 }
 
 static HTMLElement* firstNamedItem(const FormAssociatedElement::List& elementsArray,
     const WillBeHeapVector<RawPtrWillBeMember<HTMLImageElement> >* imageElementsArray, const QualifiedName& attrName, const String& name)
 {
     ASSERT(attrName == idAttr || attrName == nameAttr);
 
     for (unsigned i = 0; i < elementsArray.size(); ++i) {
         HTMLElement* element = toHTMLElement(elementsArray[i]);
@@ skipping 111 matching lines @@
         }
         const AtomicString& nameAttribute = element->getNameAttribute();
         if (!nameAttribute.isEmpty()) {
             HashSet<AtomicString>::AddResult addResult = existingNames.add(nameAttribute);
             if (addResult.isNewEntry)
                 names.append(nameAttribute);
         }
     }
 }
 
+void HTMLFormControlsCollection::trace(Visitor* visitor)
+{
+    visitor->trace(m_cachedElement);
+    HTMLCollection::trace(visitor);
 }
+
+}