One accessibility tree per frame.

third_party/WebKit/Source/core/frame/LocalFrame.h

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999-2001 Lars Knoll <knoll@kde.org>
  *                     1999-2001 Antti Koivisto <koivisto@kde.org>
  *                     2000-2001 Simon Hausmann <hausmann@kde.org>
  *                     2000-2001 Dirk Mueller <mueller@kde.org>
  *                     2000 Stefan Schimanski <1Stein@gmx.de>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2008 Eric Seidel <eric@webkit.org>
@@ skipping 79 matching lines @@
     // Frame overrides:
     ~LocalFrame() override;
     DECLARE_VIRTUAL_TRACE();
     bool isLocalFrame() const override { return true; }
     DOMWindow* domWindow() const override;
     WindowProxy* windowProxy(DOMWrapperWorld&) override;
     void navigate(Document& originDocument, const KURL&, bool replaceCurrentItem, UserGestureStatus) override;
     void navigate(const FrameLoadRequest&) override;
     void reload(FrameLoadType, ClientRedirectPolicy) override;
     void detach(FrameDetachType) override;
-    void disconnectOwnerElement() override;
     bool shouldClose() override;
     SecurityContext* securityContext() const override;
     void printNavigationErrorMessage(const Frame&, const char* reason) override;
     bool prepareForCommit() override;
 
     void willDetachFrameHost();
 
     LocalDOMWindow* localDOMWindow() const;
     void setDOMWindow(PassRefPtrWillBeRawPtr<LocalDOMWindow>);
     FrameView* view() const;
@@ skipping 202 matching lines @@
     explicit FrameNavigationDisabler(LocalFrame&);
     ~FrameNavigationDisabler();
 
 private:
     RawPtrWillBeMember<LocalFrame> m_frame;
 };
 
 } // namespace blink
 
 #endif // LocalFrame_h