Oilpan: Prepare moving AXObject to heap

Source/modules/accessibility/AXScrollView.cpp

Index: Source/modules/accessibility/AXScrollView.cpp
diff --git a/Source/modules/accessibility/AXScrollView.cpp b/Source/modules/accessibility/AXScrollView.cpp
index e3e6aaefce1d9b9c6785eaab80e6fb5ddb02e551..abfa02a50399c34cf502ffe65b88ed6a8bcd3e2e 100644
--- a/Source/modules/accessibility/AXScrollView.cpp
+++ b/Source/modules/accessibility/AXScrollView.cpp
@@ -43,18 +43,18 @@ AXScrollView::AXScrollView(FrameView* view, AXObjectCacheImpl& axObjectCache)
 
 AXScrollView::~AXScrollView()
 {
-    ASSERT(isDetached());
+    ASSERT(!m_scrollView);
 }
 
 void AXScrollView::detach()
 {
     AXObject::detach();
-    m_scrollView = 0;
+    m_scrollView = nullptr;
 }
 
-PassRefPtr<AXScrollView> AXScrollView::create(FrameView* view, AXObjectCacheImpl& axObjectCache)
+PassRefPtrWillBeRawPtr<AXScrollView> AXScrollView::create(FrameView* view, AXObjectCacheImpl& axObjectCache)
 {
-    return adoptRef(new AXScrollView(view, axObjectCache));
+    return adoptRefWillBeNoop(new AXScrollView(view, axObjectCache));
 }
 
 AXObject* AXScrollView::scrollBar(AccessibilityOrientation orientation)
@@ -253,4 +253,12 @@ ScrollableArea* AXScrollView::getScrollableAreaIfScrollable() const
     return m_scrollView;
 }
 
+DEFINE_TRACE(AXScrollView)
+{
+    visitor->trace(m_scrollView);
+    visitor->trace(m_horizontalScrollbar);
+    visitor->trace(m_verticalScrollbar);
+    AXObject::trace(visitor);
+}
+
 } // namespace blink