Oilpan: Prepare moving AXObject to heap

Source/modules/accessibility/AXObject.cpp

Index: Source/modules/accessibility/AXObject.cpp
diff --git a/Source/modules/accessibility/AXObject.cpp b/Source/modules/accessibility/AXObject.cpp
index 6c614bc316af40c592fb7ac80277f6d05df46665..9ee3b92656df40c287bad2a23b2fbd2254e2cb17 100644
--- a/Source/modules/accessibility/AXObject.cpp
+++ b/Source/modules/accessibility/AXObject.cpp
@@ -367,7 +367,7 @@ AXObject::AXObject(AXObjectCacheImpl* axObjectCache)
     , m_role(UnknownRole)
     , m_lastKnownIsIgnoredValue(DefaultBehavior)
     , m_detached(false)
-    , m_parent(0)
+    , m_parent(nullptr)
     , m_lastModificationCount(-1)
     , m_cachedIsIgnored(false)
     , m_cachedIsInertOrAriaHidden(false)
@@ -375,14 +375,16 @@ AXObject::AXObject(AXObjectCacheImpl* axObjectCache)
     , m_cachedIsDescendantOfDisabledNode(false)
     , m_cachedHasInheritedPresentationalRole(false)
     , m_cachedIsPresentationalChild(false)
-    , m_cachedLiveRegionRoot(0)
+    , m_cachedLiveRegionRoot(nullptr)
     , m_axObjectCache(axObjectCache)
 {
 }
 
 AXObject::~AXObject()
 {
+#if !ENABLE(OILPAN)
     ASSERT(isDetached());
+#endif
 }
 
 void AXObject::detach()
@@ -1361,4 +1363,12 @@ const AtomicString& AXObject::internalRoleName(AccessibilityRole role)
     return internalRoleNameVector->at(role);
 }
 
+DEFINE_TRACE(AXObject)
+{
+    visitor->trace(m_children);
+    visitor->trace(m_parent);
+    visitor->trace(m_cachedLiveRegionRoot);
+    visitor->trace(m_axObjectCache);
+}
+
 } // namespace blink