Oilpan: Prepare to move RenderObject and RenderObjectChildList to Oilpan heap.

Source/core/rendering/RenderMenuList.cpp

Index: Source/core/rendering/RenderMenuList.cpp
diff --git a/Source/core/rendering/RenderMenuList.cpp b/Source/core/rendering/RenderMenuList.cpp
index a07945d60ec81df946b13d548e516c437a2e9d5f..7dcec918e209c0c99b0422a251fe8bc7d4da968d 100644
--- a/Source/core/rendering/RenderMenuList.cpp
+++ b/Source/core/rendering/RenderMenuList.cpp
@@ -53,8 +53,8 @@ using namespace HTMLNames;
 
 RenderMenuList::RenderMenuList(Element* element)
     : RenderFlexibleBox(element)
-    , m_buttonText(0)
-    , m_innerBlock(0)
+    , m_buttonText(nullptr)
+    , m_innerBlock(nullptr)
     , m_optionsChanged(true)
     , m_optionsWidth(0)
     , m_lastActiveIndex(-1)
@@ -70,6 +70,13 @@ RenderMenuList::~RenderMenuList()
     m_popup = nullptr;
 }
 
+void RenderMenuList::trace(Visitor* visitor)
+{
+    visitor->trace(m_buttonText);
+    visitor->trace(m_innerBlock);
+    RenderFlexibleBox::trace(visitor);
+}
+
 // FIXME: Instead of this hack we should add a ShadowRoot to <select> with no insertion point
 // to prevent children from rendering.
 bool RenderMenuList::isChildAllowed(RenderObject* object, RenderStyle*) const
@@ -139,7 +146,7 @@ void RenderMenuList::removeChild(RenderObject* oldChild)
 {
     if (oldChild == m_innerBlock || !m_innerBlock) {
         RenderFlexibleBox::removeChild(oldChild);
-        m_innerBlock = 0;
+        m_innerBlock = nullptr;
     } else
         m_innerBlock->removeChild(oldChild);
 }
@@ -536,7 +543,7 @@ void RenderMenuList::getItemBackgroundColor(unsigned listIndex, Color& itemBackg
 
 PopupMenuStyle RenderMenuList::menuStyle() const
 {
-    const RenderObject* o = m_innerBlock ? m_innerBlock : this;
+    const RenderObject* o = m_innerBlock ? m_innerBlock.get() : this;
     const RenderStyle* s = o->style();
     return PopupMenuStyle(o->resolveColor(CSSPropertyColor), o->resolveColor(CSSPropertyBackgroundColor), s->font(), s->visibility() == VISIBLE,
         s->display() == NONE, s->textIndent(), style()->direction(), isOverride(style()->unicodeBidi()));