Oilpan: Prepare to move AXObjectCache to the heap

Source/modules/accessibility/AXObjectCacheImpl.cpp

Index: Source/modules/accessibility/AXObjectCacheImpl.cpp
diff --git a/Source/modules/accessibility/AXObjectCacheImpl.cpp b/Source/modules/accessibility/AXObjectCacheImpl.cpp
index 3a0f1f8bdd7785ce33fc395bf040adbbedc088e8..a9ce94309716e1ca7885c5466cef259a06ab5d20 100644
--- a/Source/modules/accessibility/AXObjectCacheImpl.cpp
+++ b/Source/modules/accessibility/AXObjectCacheImpl.cpp
@@ -84,20 +84,28 @@ namespace blink {
 using namespace HTMLNames;
 
 // static
-AXObjectCache* AXObjectCacheImpl::create(Document& document)
+PassOwnPtrWillBeRawPtr<AXObjectCache> AXObjectCacheImpl::create(Document& document)
 {
-    return new AXObjectCacheImpl(document);
+    return adoptPtrWillBeNoop(new AXObjectCacheImpl(document));
 }
 
 AXObjectCacheImpl::AXObjectCacheImpl(Document& document)
     : m_document(document)
     , m_modificationCount(0)
+#if ENABLE(ASSERT)
+    , m_hasBeenDisposed(false)
+#endif
     , m_notificationPostTimer(this, &AXObjectCacheImpl::notificationPostTimerFired)
 {
 }
 
 AXObjectCacheImpl::~AXObjectCacheImpl()
 {
+    ASSERT(m_hasBeenDisposed);
+}
+
+void AXObjectCacheImpl::dispose()
+{
     m_notificationPostTimer.stop();
 
     HashMap<AXID, RefPtr<AXObject>>::iterator end = m_objects.end();
@@ -106,6 +114,10 @@ AXObjectCacheImpl::~AXObjectCacheImpl()
         obj->detach();
         removeAXID(obj);
     }
+
+#if ENABLE(ASSERT)
+    m_hasBeenDisposed = true;
+#endif
 }
 
 AXObject* AXObjectCacheImpl::root()
@@ -1353,4 +1365,10 @@ void AXObjectCacheImpl::setCanvasObjectBounds(Element* element, const LayoutRect
     obj->setElementRect(rect);
 }
 
+DEFINE_TRACE(AXObjectCacheImpl)
+{
+    visitor->template registerWeakMembers<AXObjectCacheImpl, &AXObjectCacheImpl::clearWeakMembers>(this);
+    AXObjectCache::trace(visitor);
+}
+
 } // namespace blink