Move Frame to the Oilpan heap.

Source/core/frame/FrameView.h

 /*
    Copyright (C) 1997 Martin Jones (mjones@kde.org)
              (C) 1998 Waldo Bastian (bastian@kde.org)
              (C) 1998, 1999 Torben Weis (weis@kde.org)
              (C) 1999 Lars Knoll (knoll@kde.org)
              (C) 1999 Antti Koivisto (koivisto@kde.org)
    Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
 
    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
@@ skipping 39 matching lines @@
 class RenderBox;
 class RenderEmbeddedObject;
 class RenderObject;
 class RenderScrollbarPart;
 class RenderStyle;
 class RenderView;
 class RenderWidget;
 
 typedef unsigned long long DOMTimeStamp;
 
+// FIXME: Oilpan: move FrameView (or ScrollView) to the heap.
 class FrameView FINAL : public ScrollView {
 public:
     friend class RenderView;
     friend class Internals;
 
     static PassRefPtr<FrameView> create(LocalFrame*);
     static PassRefPtr<FrameView> create(LocalFrame*, const IntSize& initialSize);
 
     virtual ~FrameView();
 
@@ skipping 337 matching lines @@
     static bool s_inPaintContents;
 
     LayoutSize m_size;
 
     typedef WillBeHeapHashSet<RefPtrWillBeMember<RenderEmbeddedObject> > EmbeddedObjectSet;
     WillBePersistentHeapHashSet<RefPtrWillBeMember<RenderEmbeddedObject> > m_widgetUpdateSet;
 
     // FIXME: These are just "children" of the FrameView and should be RefPtr<Widget> instead.
     WillBePersistentHeapHashSet<RefPtrWillBeMember<RenderWidget> > m_widgets;
 
-    RefPtr<LocalFrame> m_frame;
+    // Oilpan: the use of a persistent back reference 'emulates' the
+    // RefPtr-cycle that is kept between the two objects non-Oilpan.
+    //
+    // That cycle is broken when a LocalFrame is detached by
+    // FrameLoader::detachFromParent(), it then clearing its
+    // FrameView's m_frame reference by calling setView(nullptr).
+    RefPtrWillBePersistent<LocalFrame> m_frame;
 
     bool m_doFullPaintInvalidation;
 
     bool m_canHaveScrollbars;
     unsigned m_slowRepaintObjectCount;
 
     bool m_hasPendingLayout;
     RenderObject* m_layoutSubtreeRoot;
 
     bool m_layoutSchedulingEnabled;
@@ skipping 107 matching lines @@
         m_view->setCanInvalidatePaintDuringPerformLayout(m_originalValue);
     }
 private:
     FrameView* m_view;
     bool m_originalValue;
 };
 
 } // namespace blink
 
 #endif // FrameView_h