Simplify DOMWindowProperty and its unregistration.

Source/core/frame/DOMWindowProperty.cpp

Index: Source/core/frame/DOMWindowProperty.cpp
diff --git a/Source/core/frame/DOMWindowProperty.cpp b/Source/core/frame/DOMWindowProperty.cpp
index d64c29ae93e6c9337126c51b523faf92cfcf4b4f..c6f25305fff00e31fcb0242026b1fc8a878fc39b 100644
--- a/Source/core/frame/DOMWindowProperty.cpp
+++ b/Source/core/frame/DOMWindowProperty.cpp
@@ -34,39 +34,24 @@ namespace blink {
 
 DOMWindowProperty::DOMWindowProperty(LocalFrame* frame)
     : m_frame(frame)
-    , m_associatedDOMWindow(nullptr)
 {
     // FIXME: For now it *is* acceptable for a DOMWindowProperty to be created with a null frame.
     // See fast/dom/navigator-detached-no-crash.html for the recipe.
     // We should fix that.  <rdar://problem/11567132>
-    if (m_frame) {
-        m_associatedDOMWindow = m_frame->domWindow();
-        m_associatedDOMWindow->registerProperty(this);
-    }
+    if (m_frame)
+        m_frame->domWindow()->registerProperty(this);
 }
 
-#if !ENABLE(OILPAN)
-DOMWindowProperty::~DOMWindowProperty()
-{
-    if (m_associatedDOMWindow)
-        m_associatedDOMWindow->unregisterProperty(this);
-
-    m_associatedDOMWindow = nullptr;
-    m_frame = nullptr;
-}
-#endif
+DEFINE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(DOMWindowProperty);
 
 void DOMWindowProperty::willDestroyGlobalObjectInFrame()
 {
     // If the property is getting this callback it must have been created with a LocalFrame/LocalDOMWindow and it should still have them.
     ASSERT(m_frame);
-    ASSERT(m_associatedDOMWindow);
 
-    // DOMWindowProperty lifetime isn't tied directly to the LocalDOMWindow itself so it is important that it unregister
-    // itself from any LocalDOMWindow it is associated with if that LocalDOMWindow is going away.
-    if (m_associatedDOMWindow)
-        m_associatedDOMWindow->unregisterProperty(this);
-    m_associatedDOMWindow = nullptr;
+    // DOMWindowProperty's registered lifetime is controlled by LocalDOMWindow. After
+    // the willDestroyGlobalObjectInFrame() notifications, LocalDOMWindow clears out
+    // all registrations. Hence no need to unregister.
     m_frame = nullptr;
 }
 
@@ -74,12 +59,6 @@ void DOMWindowProperty::willDetachGlobalObjectFromFrame()
 {
     // If the property is getting this callback it must have been created with a LocalFrame/LocalDOMWindow and it should still have them.
     ASSERT(m_frame);
-    ASSERT(m_associatedDOMWindow);
 }
 
-void DOMWindowProperty::trace(Visitor* visitor)
-{
-    visitor->trace(m_associatedDOMWindow);
-}
-
-}
+} // namespace blink